Proposal ID: 09_0003

Principal Investigator: Curtis DeWitt (USRA/SOFIA)

Title: Resolving water vapor absorption in the circumstellar disks of FU Ori stars

Abstract: FU Ori, V1057 Cyg and V883 Ori are archetypal FUor objects, a class of young, low-mass stars defined by massive accretion events causing 4-6 magnitude brightness increases. The accretion-caused heating of the disk results in a disk photosphere that dominates the system luminosity. Because of the decrease in disk temperature and increase in disk surface area with increasing radius, the observed effective temperature and absorption line widths depend on the wavelength of the observation. FUors present a unique opportunity to probe young disk atmospheres because of their unusual disk vertical temperature profile. Using R=100 spectroscopy with IRS/Spitzer, Green et al. 2006 report the appearance of water vapor absorption bands in FU Ori, V1057 Cyg and in other FUors. We will confirm this identification with EXES in medium resolution mode and resolve individual water vapor lines, which will unveil the kinematics and temperatures of the absorbing gas. By comparing the results of three FUors with different luminosity decay timescales, we will begin to investigate the evolution of disk chemistry following rapid accretion events.

Proposal ID: 09_0005

Principal Investigator: William Vacca (USRA)

Title: Tracing the Atomic Gas Component of the Galactic Wind in the Prototypical Starburst Galaxy He 2-10

Abstract: Mass outflow, in the form of a galactic wind, has been recognized to be a fairly common phenomenon among starburst galaxies. Powered by the radiation and mechanical energy and momentum of the massive stars formed during the starburst and their subsequent supernovae, galactic winds transport material out of the galaxies and into the intergalactic medium, enhancing its dust content and metallicity. These winds also play a pivotal role in the evolution of their host galaxies: by driving material out of a galaxy, they regulate star formation (feedback) and can affect the chemical evolution of low mass galaxies. We are requesting time to obtain deep observations using SOFIA/FIFI-LS of four fields in the outskirts of He 2-10, where Halpha images reveal the presence of gas outflow, in the form of a galactic wind. We propose to image these fields in the lines of [O III] 52 and 88, [O I] 145, and [C II] 158 microns, all of which trace the cool atomic gas component. We will compare these observations with the H alpha images (which trace the hot, shocked gas) to determine the relative spatial distributions of the cool and hot gas components, and therefore the determine if the cooler gas component is coupled to the hot gas. The [O III] line ratio provides an estimate of the electron density. We will combine the proposed observations with previously obtained FIFI-LS GTO data to generate a spatial map of the density and trace its value from the central starburst into the galactic wind. The combination of the [O I], [O III], and [C II] data will allow us to carry out a PDR analysis of the material in the wind and determine the gas properties. This will then provide insights to the nature and structure of the galactic wind, including the total energy and mass involved and the source of the ionization (shocks vs photoionization). We will then compare the properties of the galactic wind in He 2-10 with those of the wind in M82. Finally, we will use the [C II] map to search for the atomic gas component corresponding to the CO tail previously detected in this object.

Proposal ID: 09_0006

Principal Investigator: Nicole Karnath (SOFIA)

Title: FORCAST Imaging and Spectroscopy of Intermediate Luminosity Protostars

Abstract: Intermediate-mass protostars bridges the gap between low- and high-mass protostars. They are likely an important source of feedback in molecular clouds, are the progenitors of planetary systems that are now being detected around intermediate-mass stars, and may also serve as tracers of star formation in JWST observations of nearby galaxies. Our understanding of these protostars is hindered by the lack of a well-characterized sample of these rare protostars in the nearest 1 kpc, where they can be studied in detail. We propose FORCAST imaging and spectroscopy of 46 intermediate-luminosity protostars across several star forming regions. These targets will increase the number of well-characterized SEDs of intermediate luminosity protostars from 19 to 65 and yield a statistically significant sample to study the bridge between low- and high-mass star formation. FORCAST is the only instrument that can measure the 20-40 um SED of these protostars. This region is sensitive to the density of the infalling envelope -- and hence is an important evolutionary diagnostic. With radiative transfer models, and combined with other far-IR to sub-mm data, these data are essential for constraining luminosities, accretion rates, and infall rates. Following the example of studies of low- and high-mass star formation, this well-characterized sample will serve as the foundation of future studies with ALMA, SOFIA, and other telescopes. With Cycle 9 as potentially being the final opportunity to use FORCAST, it is essential to obtain photometry and observe these bright targets that are only available with FORCAST and no other observatory.

Proposal ID: 09_0008

Principal Investigator: Dariusz Lis (JPL)

Title: D/H Ratio in Cometary Water: Understanding the Origin of Earth’s Oceans

Abstract: Comets contain some of the most pristine materials left over from the formation of the Solar System. Measurements of the D/H ratio in cometary water provide key constraints on the origin and thermal history of water in the Solar System, and the contribution of comets to Earth's oceans. The 4GREAT instrument on SOFIA allows very accurate measurements of the D/H ratio through nearly-simultaneous observations of the low-energy rotational transitions of HDO at 509 GHz HDO and H218O at 547 GHz. We will use this instrument to measure the D/H ratio in a ToO comet with activity level comparable to that of comet 46P/Wirtanen, which was observed by SOFIA in December 2018 using the same instrument. The data analysis and interpretation will follow the procedures successfully applied to the observations of comet Wirtanen, in which a terrestrial D/H ratio was measured by SOFIA. Well-tested excitation models will be used to convert the observed line intensities to molecular production rates. Only SOFIA allows nearly-simultaneous observations of the low-energy HDO and H218O in a very similar field of view. This significantly simplifies the analysis and decreases measurement uncertainties. Based on historical average, we expect about one comet per year to be bright enough for HDO to be detectable with SOFIA. Over its remaining lifetime, SOFIA can thus significantly increase the number of existing D/H measurements, providing key observational constraints for understanding Earth's habitability. This research is perfectly aligned with the strategic objective of the DISCOVER theme of the NASA 2018 Strategic Plan: "Understand the Sun, Earth, Solar System, and Universe." The latest Planetary Decadal Survey Vision and Voyages explicitly identified "determining the deuterium/hydrogen and other crucial isotopic ratios in multiple comets" as key measurements for understanding Solar System beginnings.

Proposal ID: 09_0012

Principal Investigator: Asantha Cooray (University of California Irvine)

Title: Are local ULIRGs low in metals? Testing a new metallicity diagnostic with FIFI-LS

Abstract: A comprehensive study of the physical properties of low-z ultra luminous infrared galaxies (ULIRGs), specifically their interstellar medium (ISM), is critical to understanding the evolution of >L* galaxies and active galactic nuclei across cosmic time. ULIRGs at low redshifts are central to this endeavor, as they establish a baseline from which to measure evolution with redshift in the ULIRG population. In Cycle 9 FIFI-LS observations will be aimed at measuring far-IR (FIR) [OIII]52, [NIII]57, [NII]122 um lines of 10 ULIRGs from IRAS at 0.01 < z < 0.13. The proposed observations will provide comprehensive diagnostics of the physical conditions of the ISM such as the gas density, radiation field intensity, and metallicity that is much less susceptible to extinction than traditionally used UV/optical transitions. We will be able to apply the excellent FIR metallicity diagnostic, ([OIII]52+2.2[OIII]88)/[NIII]57, for the first time, which breaks the density degeneracy and reduces the scatter in the correlation to within 0.2 dex. The unprecedentedly reliable metallicity measurements will address whether ULIRGs lie below the mass-metallicity relation of star-forming galaxies as previously thought based on optical metallicity diagnostics. Along with archival Herschel/PACS+SPIRE observations, we will be able to test all the line-ratio diagnostics by comparing to models (e.g. Cloudy) and identify the best pairs to optimize future observations with ALMA for high-z analogs. This SOFIA program will open up the opportunity to increasing the sample of low-redshift (0.1 < z < 0.3) ULIRGs with the full set of FIR line observations by a factor of 2-3. This program will also demonstrate a key science program for the Origins Space Telescope that focusses on metallicity measurements out to z of 6 with results from this program potentially making an impact in development plans for SPICA in Europe and a general purpose mid/far-IR observatory in US.

Proposal ID: 09_0013

Principal Investigator: Paul Goldsmith (JPL)

Title: [OI]146 Micron Observations: Accurate modeling of [OI] Emission Absorption and PDR Structure

Abstract: Massive star formation has a profound impact on galactic evolution due to the impact on the interstellar medium of the resulting radiation field and winds. Among the most important probes and the most important coolant of warm, dense photon dominated regions (PDRs) is atomic oxygen, which has two fine structure lines, [OI] 63 and 146 microns. Considerable data have been obtained on the 63 micron [OI] transition, but this line, with the atomic ground state as its lower level, has been found to be very optically thick. High resolution SOFIA/GREAT spectra reveal very clear self-absorption from foreground material. The large and uncertain optical depth compromises the ability of the 63 micron line alone to trace massive star formation. The 146 micron line, in contrast, has its lower level 228 K above ground, which is difficult to populate and hence this spectral line is almost always optically thin. The combination of the two lines can dramatically improve our ability to model [OI] fine structure emission and will enhance its value for understanding feedback from massive, young stars. We propose to obtain high quality spectra of both lines in a selection of Galactic sources with massive star formation. We will use OTF honeycomb mapping to fill in observations of the 63 micron line made with the HFA over the beam size of the 146 micron line. We will also observe the [CII] fine structure line in the second polarization of the LFA, which together with the [OI] lines, can determine the temperature and density of the PDR emission region. This will be the first program ever to obtain high-quality velocity-resolved spectra of both [OI] lines in a statistically significant number of GMCs with massive star formation. In addition to its immediate value in studying PDRs, the results will serve as a template for interpreting Galactic and extragalactic [OI] emission, and will help guide planning for future FIR missions.

Proposal ID: 09_0015

Principal Investigator: Dariusz Lis (JPL)

Title: The Role of the Magnetic Field in the Evolution of GMCs: Star Formation in Filaments and Stellar Feedback

Abstract: Magnetic fields have long been argued to play a key role in supporting molecular clouds against gravitational collapse and consequently in reducing the rate of star formation far below that expected based on the free-fall collapse time scale. Planck dust polarization maps revealed a dramatic change in the alignment between the magnetic field and dense gas, from parallel in the diffuse regions to perpendicular in dense supercritical filaments and ridges. Such a transition should be accompanied by a corresponding change in the kinematic properties of the gas, which can be investigated through a combination of wide-field dust polarization and velocity-resolved molecular line imaging at high angular resolution. A 5 square degree region in the Orion B molecular cloud has recently been imaged in 30 molecular lines at a 26” (0.05 pc) resolution. This exceptional data set enables an unprecedented characterization of the physical structure, chemistry, and dynamics of a typical star-forming GMC with a favorable geometry for studying (a) the dynamics of young HII regions and the feedback from massive stars on the surrounding gas, and (b) the role of the magnetic field in the formation and evolution of dense filaments. The small-scale magnetic field geometry is the key missing ingredient. We propose to use HAWC+ on SOFIA to measure the 154-mic and 214-mic dust polarization over a 20 x 20 arcmin region centered on NGC2024, using the OTFMAP polarimetric mode to correlate changes in the magnetic field geometry with corresponding changes in the kinematic properties of the gas. This will allow directly assessing the importance of the magnetic field in star formation and stellar feedback. With the molecular data already available, this program will lead to immediate scientific results.

Proposal ID: 09_0016

Principal Investigator: Ian Stephens (Worcester State University)

Title: Guiding the Flows: A Multi-Scale SOFIA-ALMA Survey

Abstract: Recent work has shown that understanding the role of magnetic fields in star formation requires a multi-scale approach. This is particularly true for high-mass star formation, given the size of giant molecular clouds. Our team was granted an A-rated Cycle 6 ALMA program to observe polarized dust emission for 29 of the brightest high-mass star-forming sources, which allows us to probe scales of ~500 au to 0.1 pc. The observations reveal complex morphologies in a gravity-dominated environment. Large-scale polarization measurements are needed to understand the multi-scale importance of magnetic fields in a statistical sample of high-mass sources. For a statistically robust sample, we plan to combine archival HAWC+ data (3 sources) with new observations of any 7 of these ALMA regions using Band D (154 um) polarimetric observations. These observations will probe the magnetic field at scales of ~0.1 pc to few pc. We will analyze the balance of energies (magnetic, turbulent, and gravity) at both large and small scales to determine if the energy balance is consistent between scales and how it affects the underlying fragmentation. We will determine if the complex morphologies we see at ALMA scales are also seen with SOFIA at the large-scale, or if the morphology is due to more local effect such as rotation and feedback. Note that this is a Survey Program so we only need any 7 of the 22 proposed targets, which amounts to a total of ~5 hours.

Proposal ID: 09_0019

Principal Investigator: Pak Shing Li (University of California at Berkeley)

Title: The Role of Magnetic Fields in the Formation of Starless Cores in Filamentary Molecular Clouds

Abstract: In the past few years, several attempts have been made to resolve the central regions and possibly detect multiplicity in starless cores. Recently Caselli et al. (2019) have reported the detection of substructure in the central 1000 AU region of L1544. Using ALMA Cycle 6 results, substructures are detected in the central regions of four starless cores, including G208.68-19.20 and G209.29-19.65 in the Orion complex at 1" FWHM, corresponding to a scale of 400 AU. In order to study the role of magnetic fields in the formation of high density starless cores, where stars form, we need information on the physical environment around such cores, which are usually connected with filamentary substructures inside molecular clouds. We propose to observe the polarization in two ~ 1 pc regions of filamentary molecular clouds surrounding the two starless cores G208.68-19.20 and G209.29-19.65 using HAWC+ at Band E to reach a resolution ~ 7000 AU at a distance of 400 pc. With the SMA polarization data and ALMA polarization observation focusing on these two cores at the resolution of 400 AU, we shall have an accurate picture of the magnetic field structures from inside the starless core to a region of about 1 pc surrounding the cores. Using high resolution density and line-of-sight velocity information from NRO 45 m and ALMA Cycle 6 observations, we can infer the dynamical state of their environments. The information of dense cores formed in molecular clouds in MHD simulations shall help us determine what triggers the formation and fragmentation of dense starless cores in molecular clouds and how these cores evolve. This will provide crucial insights on the process of star formation, with implications for the star formation rate and the origin of the stellar initial mass function.

Proposal ID: 09_0020

Principal Investigator: Jorge Pineda (JPL)

Title: Probing Highly Ionized regions in Carina and G333.6-0.2 with [NIII] 57µm

Abstract: Radiative feedback from massive stars into their surrounding interstellar medium plays an important role on the regulation of star formation in galaxies, which is in turn a key driver in galaxy evolution. In the close vicinity of massive star clusters, a significant portion of the radiative energy is in extreme ultraviolet (EUV) and gives rise to a highly ionized layer adjacent to the photon dominated regions of molecular gas clouds. Characterizing the EUV layer is critical to understanding the energy balance in the ISM and the transfer of energy from stars to gas. An important probe of the EUV environment is the [N iii] fine structure line at 57 μm, because EUV photons >29.6 eV must be present to ionize nitrogen to states higher than N+ . Combining EUV probes with those at lower ionization states is critical to understand the energetics of star forming regions. We propose to map the [NIII] 57µm line with the FIFI-LS instrument on SOFIA to characterize the EUV radiation field environments in the Carina and G333.6-0.2 massive star forming regions. We will combine the FIFI-LS [N iii] observations with existing ISO, SPIFI, KAO, and SOFIA 4GREAT archival observations of [NII] 205µm and 122µm to characterize the EUV environments of massive star forming regions. These observations will provide fundamental information on the relative importance different radiative and mechanical feedback mechanisms have in regulating star formation. The Carina and G333.6-0.2 massive star formation regions will be mapped over large scales with the ASTHROS balloon in the [N ii] 122µm and [N ii] 205µm lines, enabling the construction of high spectral resolution maps of the electron density in these regions. The proposed FIFI-LS research will provide the foundation for interpreting these large scale maps of such regions. By mapping [N iii] 57µm with the FIFI-LS instrument in SOFIA we will determine the spatial extent of such highly ionized regions, and together with ancillary [N ii] data, will enable an accurate determination of the EUV and FUV field strengths, distributions, and role in the energetics between star formation and ISM.

Proposal ID: 09_0021

Principal Investigator: David Neufeld (Johns Hopkins University)

Title: Kinematics of shock-heated H2 with EXES and the conversion from para- to ortho-H2

Abstract: Shock waves are a ubiquitous phenomenon in the interstellar gas, and may cause the heating, compression, dissociation, and/or ionization of the gas through which they propagate. A Cycle 6 program, conducted with the EXES instrument toward HH7, has recently reported velocity-resolved observations of the mid-IR H2 emission lines that dominate the emission from shocks propagating in molecular gas. Those observations revealed, for the first time, the presence of velocity shifts between lines of ortho-H2 [S(5) and S(7)] and those of para-H2 [S(4) and S(6)], bearing witness to the conversion of para-H2 to ortho-H2 within the shock wave, and providing among the best evidence yet obtained for the existence of C-type shock waves in which the flow velocity varies continuously. Motivated by this discovery of H2 ortho-para velocity shifts in a single source in Cycle 6, we will perform observations of the H2 S(4) – S(7) emission lines from three additional shocked regions that span a range of astrophysical environments including supernova remnants and protostellar outflows. By interpreting the observations in the context of state-of-the-art shock models, we will place unique constraints on the physics of molecular shocks.

Proposal ID: 09_0022

Principal Investigator: Enrique Lopez-Rodriguez (SOFIA Science Center at NASA Ames)

Title: Revealing how large-scale magnetic fields arise from the interstellar turbulence through a 0.5 sqdeg. magnetic field map of the Large Magellanic Cloud

Abstract: The understanding of the origin and morphology of the magnetic fields (B-fields) in galaxies is crucial for a complete picture of galaxy evolution. The B-fields accelerate and confine cosmic rays, trigger star forming regions, and exert pressure to balance gas against gravity. These B-fields are thought to be generated by galactic dynamos, which rely on small-scale turbulent fields and differential rotation of the galactic disk to amplify and order the B-fields. Small-scale fields must be quantified to understand the amplification of the mean-field dynamo generating the observed large-scale fields from the diffuse synchrotron emission by radio in nearby galaxies and dust polarization by Planck in the Milky Way and Large Magellanic Cloud (LMC). However, the physical mechanisms connecting small-to-large-scale fields in dynamo theories are poorly understood. The LMC provides the bridge between the Milky Way and nearby galaxies. Although a large-scale field may be present in the LMC, radio and Planck observations show irregularities in the southeast region of the galaxy mainly due to strong star forming regions and/or tidal effects from the SMC and the Milky Way. The small-scale fields have not been measured, which may play a crucial role in 1) the dynamics of the underlying star forming regions in the southeast of the galaxy, 2) the galactic dynamo of the LMC, and 3) potential outflows along the filaments. As dynamos convert kinetic energy into magnetic energy, our goal is to compare the spectra of magnetic and kinetic energies, and quantify how the B-fields plays a role in star formation, and how in turn star formation locally amplifies the B-fields. HAWC+ will produce the finest magnetic field map at a resolution of 3.4 pc covering a 0.5x1 sqdeg. (0.45x0.9 kpc) area of the southeastern region of the LMC. We will compute the small-scale magnetic field strength and morphology maps and compare it with the large-sale field from radio and Planck polarimetric observations, which will allow us to test dynamo theories. We will test whether small-scale turbulent B-field misalignment is important in the generation of large-scale fields and allow field strength estimates, which are both key unknown factors that strongly affect galaxy evolution.

Proposal ID: 09_0023

Principal Investigator: Tucker Jones (University of California; Davis)

Title: Accurate chemical abundance measurements: from z=0 to the reionization epoch

Abstract: The gas-phase metallicity of galaxies encodes information about current and past gas inflows, outflows, and star formation. Accordingly, obtaining accurate metallicity measurements for large samples of galaxies is a major goal of galaxy formation and evolution studies. However, current results suffer from large systematic uncertainty in the absolute metallicity scale, revealed by disagreement between different direct measurement techniques. This disagreement can plausibly be explained by fluctuations in the gas temperature within HII regions, but an independent test is needed to determine whether this is indeed the case. We propose to use the unique capabilities of FIFI-LS onboard SOFIA to obtain measurements of the diagnostic [OIII] 52 um emission line for a sample of carefully-selected local HII regions with high-quality optical spectra. The addition of [OIII] 52 um data will provide an independent determination of the magnitude of temperature fluctuations and the absolute metallicity scale. The results will have an immediate benefit of eliminating the dominant systematic uncertainty in metallicity measurements of >100,000 galaxies at z=0 and >1,000 at z>1. Furthermore, these measurements will provide the framework necessary to combine ALMA measurements of far-IR lines with JWST rest-optical spectra to determine accurate metallicities at z>6 in the epoch of reionization. We will simultaneously observe the [CII] 158 um line to aid in understanding extremely high far-IR [OIII]/[CII] ratios found for z>6 galaxies using ALMA.

Proposal ID: 09_0025

Principal Investigator: Matthew Millard (University of Texas at Arlington)

Title: FIR Spectroscopic Study of High Velocity Ejecta Assocated with Cold Dust in Young Supernova Remnants

Abstract: The large quantity of dust observed in high-z galaxies raises a fundamental astrophysical question on the origin of dust in the Universe, since AGB stars, which are thought to produce most interstellar dust, are too old to have evolved in high-z galaxies. The Core-collapse (CC) SN, the explosion of a massive star, can occur within millions of years after star formation, and thus may be a significant contributor to dust formation in the early Universe. Recently, Spitzer and Herschel observations of a few young CC supernova remnants (SNRs) showed that CC SNe are indeed a dust factory. However, due to a small sample size in the previous works, it is difficult to constrain the amount of the dust formed in CC SNe. Identifying SN ejecta and the associated dust formation in a larger sample of young CC SNRs are essential to constrain the contribution of CC SNe to interstellar dust production. Searching for bright FIR emission lines ([O III] at 52 and 88, and [C II] at 157 micron) in the archival ISO LWS data, we identified two young CC SNRs (besides the previously studied sample) as excellent candidates for such a study. These strong emission lines are similar to those from high velocity ejecta detected in CC SNRs in previous works. Some of these ISO-detected lines appear to show broadening, while some others are not broadened within the ISO spectral resolutions. We propose to observe these bright candidate ejecta lines in these CC SNRs with the SOFIA FIFI-LS which offers superior spectral resolutions and higher sensitivity than the ISO/LWS. Our goals are i) to identify high velocity ejecta emission; ii) to estimate elemental ejecta masses; iii) to correlate detected ejecta elements and dust composition; and iv) to estimate efficiency of dust formation by comparing ejecta and dust masses. Our proposed study will help address the question of whether CC SNe are the primary dust producers in the early Universe.

Proposal ID: 09_0027

Principal Investigator: Kate Su (University of Arizona)

Title: Constraining Planetesimal Collisions in the Terrestrial Planet Zone of HD 166191

Abstract: Variable debris disks, discovered with Spitzer, give new insights to the collisional merging of planetary embryos and oligarchs over a period of about 200 Myr after protoplanetary disks have cleared. They have let us set timescales for the clearing of collisional debris, critical to understand the duty cycle of infrared excesses and the incidence of major planetesimal collisions. One system, HD 166191, has recently undergone a major series of collisions and exhibited an anti-correlated disk variations between 3-5 micron and 8-20 micron regions, suggesting a complex evolution connection between mm-sized vapour condensates and their sub-micron-sized products. HD 166191 provides an excellent opportunity to further refine our understanding of disk variability during terrestrial planet building phase. This program aims to obtain a third epoch mid-infrared spectrum with SOFIA to track the debris evolution, allowing a quantitative comparison of the amount and composition of small grains between the quiescent, the active and the post-impact states of the system. The proposed observation, along with the existing SOFIA data, has great synergies with the Spitzer data, leaving a legacy for future observations with JWST.

Proposal ID: 09_0029

Principal Investigator: Robert Gehrz (University of Minnesota - Twin Cities)

Title: SOFIA Target of Opportunity (ToO) Observations of Bright Classical Novae in Outburst

Abstract: Classical novae (CNe) contribute to Galactic chemical evolution by injecting dust grains and gas into the interstellar medium (ISM). We propose to obtain SOFIA FORCAST spectra of CNe that go into outburst during Cycle 9. The proposed observations can determine critical physical parameters that characterize the explosion and CNe contributions to the ISM. Our observations will yield the mass ejected, the mineralogy and abundance of the dust grains, and gas phase abundances of LiCNONeMgAl metals in the ejecta. The 5 to 37 micron spectral range of FORCAST grisms enables complete and simultaneous access to the many dust and gas emission features. Any nova brighter than 8th magnitude at visual maximum can trigger our ToO program when supporting optical/IR ground-based or space-based observations indicate that the nova is in 1) a dust formation and growth phase, 2) a forbidden line emission development phase, or 3) the early free-free expansion phase.

Proposal ID: 09_0030

Principal Investigator: Christopher Clark (Space Telescope Science Institute)

Title: The First Unambiguous Measurement of Carbon Depletion via 158μm [CII] Absorption

Abstract: Context: Depletion of metals onto dust grains affects our ability to probe the cold ISM of galaxies. The division of metals between the gas and dust phases dictates how we interpret galaxies' chemical evolution, metallicity and radiative transfer properties. And our ability to exploit dust emission as a tracer of galaxies' gas and metal content requires us to understand its composition. But embarrassingly, despite carbon being a primary constituent of dust, its depletion (and how its depletion varies) is barely constrained. Aims: Until now, estimates of gas-phase carbon abundance have depended upon UV absorption features that are either very weak or highly saturated; the resulting abundances conflict with each other, and are few in number. We propose to use 158µm [CII] absorption to at last make unambiguous measurements of ISM carbon abundance and depletion in the Milky Way. Methods: We intend to observe the 158μm absorption feature due to [CII] along sightlines to three external galaxies with bright far-infrared continuum, to directly determine the Galactic carbon column along those sightlines. Synergies: This program complements abundances measured for other elements in the UV (Hubble), and paves the way for future facilities (Origins & SPICA) that will be able to probe many more sightlines than SOFIA, sample much denser ISM than accessible in the UV, and enable measurements in other galaxies. Anticipated Results: The first unambiguous measurements of ISM carbon abundance and depletion, settling long-standing uncertainty.

Proposal ID: 09_0031

Principal Investigator: Joseph Hora (Center for Astrophysics | Harvard & Smithsonian)

Title: Investigating the Effects of Environment on Star Formation: the Outer Galaxy Cluster G104.52+01.24

Abstract: High mass star formation is much less well understood than low mass star formation. This is in part due to the greater distance, extinction and confusion toward regions of high mass star formation and the rapid evolution of high mass protostars and the difficulty of finding such objects in the earliest stages of their evolution. In order to investigate the changes in the star formation process caused by the differences in the environment (metallicity, temperature, density, etc.) where the star formation is taking place, we propose to use FORCAST on SOFIA to image the central source and parts of the outer Galaxy cluster G104.52+01.24 in the 20-40 µm range. The observations will complement existing Spitzer, Herschel, and near-IR data, allowing us to understand the central source in this cluster. With SOFIA we will find massive protostars and study the Galactic equivalent of objects that JWST will observe in more distant Galactic regions and in other galaxies. The SOFIA results will enable us characterize the high mass cluster in the core of this molecular cloud by revealing the youngest cluster members, and determining the nature of the central source and nebula. We will also be able to examine the effect that these stars have on their surroundings through outflows and radiation, and how it is shaping the molecular cloud and triggering subsequent generations of star formation.

Proposal ID: 09_0035

Principal Investigator: Goran Sandell (Institute for Astronomy; UH Hilo)

Title: Using [CII] to probe the environment of the LkHa101 HII region reflection nebula and foreground cloud

Abstract: We propose to use the upGREAT LFA to map ~ a 4.5 arcmin region around the young B0 star LkHa101 in [CII]. The star is in the center of a large reflection nebula NGC1579 and excites the HII region S222. The star is still heavily accreting and has a strong stellar wind. The goal with these observations is a) to probe the dense PDR we expect to see in the interface between the HII region and the surrounding molecular cloud (at -3.8 km/s), b) investigate the [CII] emission in the surrounding large refection nebula (also at -3.8 km/s and c) characterize the PDR emission of the foreground dark cloud to better understand the physical condition in this unusual cloud. Modeling will be done using simple PDR models.

Proposal ID: 09_0036

Principal Investigator: Suzanne Madden (CEA)

Title: SOFIA Joint Legacy Survey of [CII] in the LMC: LMC+

Abstract: This Joint Legacy Program, LMC+, aims to determine the role of metallicity on the physical conditions of the molecular, atomic, and ionised interstellar medium, by zooming into a large region of the Magellanic Cloud that is known to have a factor of 2 lower metal abundance than the Milky Way. We propose a 1.3 deg x 0.5 deg FIFI-LS map of [CII] 158 micron and [OIII] 88 micron emission toward the most prominent large-scale star forming/molecular cloud complex in the LMC, the Southern Molecular Ridge. These far-infrared lines trace the molecular gas not traced by CO-emission (the CO-dark gas) as well as ionized gas in embedded and bursting HII regions. Even though a change in metallicity by a factor of 2 seems small, we expect to detect a factor 10 or more molecular gas mass than that seen in CO, which will be photodissociated by the LMC interstellar radiation field. The CO-gas will be in dense clumpy molecular pockets, permeated by lower density neutral interstellar medium. We will determine the mass ratio of dense molecular and more diffuse molecular/atomic gas and the porosity of the interstellar medium. This is significant, in order to estimate the star formation efficiency in the LMC and also to relate to the structure of the interstellar medium in high-redshift galaxies where the average metallicity is below solar. Only this large-scale SOFIA FIFI-LS map of this template region can bring to light the full interplay of star formation and molecular gas destruction by massive stellar radiative and wind feedback. Much of this region has recently been targeted by ALMA CO observations, to allow the comparison between conditions for the role of CO-bright vs CO-dark molecular reservoirs. This survey may also serve as a pathfinder for higher spectral resolution upGREAT observations, and observations of the energetic mid-infrared nebular species with JWST.

Proposal ID: 09_0037

Principal Investigator: B-G Andersson (USRA/SOFIA Science Center)

Title: Spinning at the Bar - The B-RAT to k-RAT transition in the Orion Bar

Abstract: Dust-induced polarization provides a powerful tool to probe interstellar and circumstellar magnetic fields if the details of the grain alignment mechanism can be fully understood. Radiative Alignment Torque (RAT) theory provides a quantitative framework for this understanding, but some aspects still needs to be quantitatively tested. One such aspect is the possibility that the reference direction for the alignment may change from the magnetic field ("B-RAT") to the radiation field k-vector ("k-RAT") in areas of strong radiation fields. Such direction changes have been claimed for protostellar disks, with CARMA and ALMA observations, and in the Orion Bar, based on earlier SOFIA/HAWC+ data, but have only been qualitatively analysed. While the Orion Bar provides a much better characterized model system to compare to ab initio RAT theory, the existing observations (Chuss et al 2019) were acquired in chop-nod mode and are therefore prone to poorly characterized off-beam contamination. Because the level of polarization in the Bar is low, the position angle rotation seen is therefore insecure. Here, we propose to re-observe the Bar and an adjacent low flux area South East of it, in scan-pol mode, to confirm the possible position angle rotation and allow detailed characterization of the transition from B-RAT to k-RAT alignment based on ab initio RAT theory.

Proposal ID: 09_0038

Principal Investigator: Matthew Malkan (UCLA)

Title: Highly Ionized Gas in AGN and Metal-poor Starbursts

Abstract: We propose FIFI spectroscopy of the crucial [O III]52µm line in two of the brightest nearby Seyfert galaxies with extremely sub-solar metallicity. Combined with our fine structure line coverage from Spitzer/IRS and Herschel/PACS, we will determine the role of abundances and N/O variations in galaxies with metal-poor starbursts and those of AGN, both of which can produce highly ionized gas. The FIFI spectroscopy of proposed active galaxies will be merged with an existing complete set of fine structure lines in metal-rich galaxies, to obtain a comprehensive sample. We will compare observations with our photoionization models, of both starbursts and AGN. In particular we will determine under what conditions the N/O abundance is changed compared to the [O/H] abundance, as is suspected to occur in the highly ionized gas in young galaxies at high redshift. Our far-IR diagnostics are superior to those based on optical lines, especially in dust-obscured galaxies. This will lay the foundation for understanding analogous galaxies at high redshift, whose far-IR fine structure lines are accessible to ALMA at its highest frequencies. The targets are already observed to have very bright forbidden fine-structure emission lines in other transitions. Based on successful observations of [OIII]52µm with FIFI in Cycle 7 in metal-poor starburst galaxies, we are therefore confident that our requested integration times will yield very high SNR (>15) detections even under the most conservative assumptions. We will use mapping observations optimised for super-resolution in the red array to simultaneously observe the blue- and red-shifted components of the OH 119um molecular flows in these galactic centers to investigate AGN feedback.

Proposal ID: 09_0039

Principal Investigator: Haojing Yan (University of Missouri-Columbia)

Title: HAWC+ Observations of Planck-selected 550 micron Peakers

Abstract: The Planck CMB mission has also provided the first all-sky survey of astrophysical sources in the sub-mm/mm regime. Of particular interest among these sources are those of red sub-mm colors that resemble dusty starbursts at high redshifts. These sources are very bright (> 200 mJy), implying extremely high luminosities (> 10^14 Lsun) if they are indeed at high-z. The natural explanation would then be that they are either galaxy clusters or gravitationally lensed individual galaxies. In either case, these sources are important because they form a complete sample of the most extreme sources in the universe from an all-sky survey. Follow-up studies, however, are hindered by the very coarse spatial resolution of Planck (~ 5'-5.5' at 350--850 micron), and higher resolution imaging at similar wavelengths is necessary to pinpoint the exact source locations. A few programs have been carried for this purpose using the early and the first release of Planck compact sources. Using the Second Planck Catalog of Compact Sources (PCCS2) based on the full Planck mission data, we have selected a sample of five "550 micron peakers" whose SED peaks are at 550 micron. Two of these five objects are in the directions suitable for SOFIA observations, and here we propose HAWC+ total intensity measurements in E, D and C-bands. Our results will facilitate the interpretation of these brightest sub-mm sources in the universe by determining whether they are lensed or clusters and by enabling a full SED analysis. Very importantly, the results will also provide positions accurate enough for future follow-up studies at other wavelengths. We request 8.2 hrs in total.

Proposal ID: 09_0041

Principal Investigator: Cristian Guevara (I Physikalisches Institut - Universität zu Köln)

Title: [12CII]/[13CII] isotopic abundance ratio in M17SW and NGC 1977

Abstract: Our observations with the 14 pixel SOFIA/upGREAT receiver of the [12CII] fine and [13CII] hyper-fine structure lines have shown that the [CII] is heavily affected by self-absorption effects and/or high optical depth. The observations were done at very high velocity resolution and sensitivity towards four PDRs in the Galaxy, with M17 the one with the most prominent features. This scenario can be explained with a double layered model, with a high density [CII] background layer in emission, absorbed by a cold, lower density foreground [CII] layer. Both, the extremely high column densities of the warm emitting gas and even the nature of the colder foreground absorption gas, are very hard to explain in the context of standards PDR models. A key element for this analysis is the [12CII]/[13CII] abundance ratio. The abundance ratio allows us to scale up the [13CII] line and therefore, transform it to an equivalent optically thin [12CII] emission. This equivalent emission is compared to the observed [12CII] line, for deriving the optical depth and the physical properties of the gas. We have assumed that the [12CII]/[ 13CII] isotopic abundance ratio is the same than the 12C/13C elemental abundance ratio but this is not necessarily true. Fractionation effects could arise and increase the abundance ratio. The high sensitivity of GREAT now allow us to directly derive the [12CII]/[13CII] isotopic abundance ratio from the comparison of the line wing emission of both isotopes through deep integrations and to detect fractionation signs if present. Neither measurements of the carbon isotopic abundance ratio nor detection of fractionation for [CII] has ever been done before. We have selected two regions for this analysis, M17SW and NGC 1977. Both regions present high optical depth for the [CII] line and an edge-on structure. Both regions has different physical conditions, these differences allow us to address possible dependencies of the fractionation on the environment.

Proposal ID: 09_0043

Principal Investigator: Cristian Guevara (I Physikalisches Institut)

Title: M43 and M17SW [OI] 63 and 145 µm fully sampled maps

Abstract: Our recent observations with SOFIA/upGREAT at very high velocity resolution and S/N of [12CII] and [13CII] lines have shown for a number of sources, M43 and M17 between them, that the [CII] line is optically thick and, for M17, is heavily affected by self-absorption. This is due to absorption of the background emitting layer by a colder foreground layer of [CII] associated with some velocity components of the source. Both, the high column densities of the warm emitting gas, and in particular the nature of the rapid variating colder foreground absorption gas, are very hard to explain in the context of standards PDR models. New [OI] 63 and 145 µm observations at the 7 positions observed in [CII] for M17 SW, have shown that [OI] 63 µm follows the same line profile of the self-absorbed [CII], including its absorption dips, meanwhile [OI] 145 µm shares the same line profile with the optically thin [13CII]. This phenomena motivate us to obtain fully sampled [OI] maps for both transitions for M17 and M43. M17 is one of the brightest and most massive giant molecular clouds in the Galaxy. It is illuminated by a large cluster of OB stars. It is one of the best galactic regions to study PDR structure from the exciting source to ionization source. M43 is a close-by ideal spherical nebula with a single early B type star in the center. Due to its close distance, simple spherical geometry and single ionization source, it is well suited as a simple, properly characterized source. With this proposal, we want to study the distribution of [OI] 63 and 145 µm in M17 SW and M43. We plan to do this through observations of fully sampled maps in [OI] 63 µm and [OI] 145 µm. The main goal is to map the rapid variation in the foreground absorption layer through the comparison of both [OI] lines.

Proposal ID: 09_0044

Principal Investigator: Miguel Santander-Garcia (Observatorio Astronomico Nacional)

Title: The total mass of post-common-envelope PNe

Abstract: A large fraction of stars in the Universe die as planetary nebulae (PNe). About 20% of those do so by means of a sudden event that involves the expanding envelope of the giant (AGB) star engulfing a close companion, entering a very brief (~1 year) but crucial stage known as the common envelope (CE). Drag forces then lead to the abrupt ejection of the envelope, forming the PN, which should be considerably more massive than PNe arising from single stars. However, recent measurements of the sum of ionised and molecular mass of many of these objects suggest this is not the case, with most post-CE PNe lying in the lower end of the PNe mass distribution, which is at odds with current understanding of stellar evolution. Yet, a fraction of the mass of these objects could still be in photo-dissociation regions (PDRs), mostly in the form of neutral atoms. The flux of the [C II] 157 micron line present in PDRs is known to constitute the best tool to infer their mass in PNe. We therefore request observations of [C II] 157 (and [O I] 63) micron in a sample of post-CE PNe with SOFIA/GREAT to address this question. These observations will complement existing data of the molecular and ionised contents of post-CE PNe, from recent observations with the IRAM 30m telescope and the literature. Together, they will allow us to derive total mass values for these objects, and compare them to the expected mass of the progenitor AGB envelopes. Results will also be compared to a large sample of regular PNe for which data already exist from published (ISO) or unpublished (HERSCHEL/HIFI+PACS) observations. We expect these observations to lead to a robust determination of the PDR mass in a significant sample of post-CE PNe. These are the only data still necessary to solve or convincingly confirm the discrepancy between measured and expected masses of post-CE PNe, an essential gap in our understanding of binary stellar evolution.

Proposal ID: 09_0046

Principal Investigator: Kathleen Kraemer (Boston College)

Title: The Dustiest S Stars: On the Chemical Cusp

Abstract: Context: Stars on the asymptotic giant branch (AGB) are usually dominated by either oxygen or carbon chemistry, depending on which element is more abundant in their atmospheres. This determines what dust and gas features are seen in their spectra, and hence what can be learned about their physical conditions. In S stars, the ratio is close to unity, C/O~1, which can lead to chemistries dominated by neither C nor O. This unusual chemical domain lets us probe the properties of an AGB star as it transitions from an O-rich M giant to a carbon star. Aims: We will use the FORCAST grisms on SOFIA to characterize the dust and gas in 16 of the dustiest S stars. Mid-IR observations are the best way to study processes such as dust condensation at these unusual chemistries, but prior samples are biased against dustier S stars. With our new FORCAST data, we will investigate important aspects of the S star population that those samples could not. Methods: We will obtain 5–37 μm spectra of 16 very dusty S stars in the Milky Way. We will compare their derived properties to those from the less dusty S stars, as well as to O- and C-rich samples. In particular, we will use the full S star sample to determine whether correlations between spectral features and stellar characteristics recently found in C stars using SOFIA data also apply to S stars. Synergies: These data will let us compare the characteristics of these very dusty S stars to those of the less dusty samples. Those stars already have mid-infrared spectra from older missions such as Spitzer or the Infrared Space Observatory, as do the O- and C-rich AGB stars. Anticipated Results: The data sets we will produce in this investigation include mid-IR spectra for 16 of the dustiest S stars in the Galaxy and analyses of their molecular gas and dust properties in the infrared. We will place these stars and their properties in context with the relatively dust-free S stars and the broader population of Galactic AGB stars.

Proposal ID: 09_0048

Principal Investigator: Peter Barnes (Space Science Institute)

Title: The Magnetic Keys to Star Formation

Abstract: The role of B fields in star forming (SF) clouds is still widely debated, partly due to observational challenges in measuring their strength and geometry. An important threshold from Zeeman work is the transition from magnetic to gravitational domination near densities 300 cm–3, but this transition has not been clearly defined in a well-studied cloud sample. Wide-field Planck results establish the larger-scale, lower-density geometry, but we lack systematic information connecting these giant molecular clouds (10+ pc) to data on protostellar core B fields (0.1 pc), where pc-scale cluster forming clumps dominate SF. HAWC+ provides an exciting opportunity to bridge this gap by enabling high quality, core-resolution B field mapping in the cold gas where stars form. A HAWC+ polarimetry mapping study of a representative, well-studied sample of massive molecular clumps at different evolutionary stages but a single distance will measure B fields in different SF environments and compare their importance with other physical processes. We will employ innovative new analysis techniques to maximize the science output of the HAWC+ data at the critical parsec scale, uniquely leveraged by existing multi-wavelength continuum and spectroscopic data on clumps' non-magnetic properties, plus new data from ongoing/pending projects at ALMA (massive cores, including Zeeman data) and APEX (formation of dark molecular gas). High spatial dynamic range maps of dust polarization will allow detailed mapping of B field geometries and strengths and statistical studies of magnetic properties across contiguous scales 0.1–10 pc. Combining kinematic and column density maps of the clouds' physical, chemical, and thermodynamic state from mm spectroscopy and Spitzer and Herschel images, we will compute magnetic, gravitational, & turbulent energy densities, measure the role of B fields in these settings, and define the fundamental physics driving molecular cloud evolution.

Proposal ID: 09_0051

Principal Investigator: Ravi Sankrit (Space Telescope Science Institute)

Title: The Long Term Evolution of Silicates in Symbiotic Mira Systems

Abstract: Our goal is to study the long term evolution of silicate dust in the circumstellar envelopes of oxygen-rich symbiotic Miras, which consist of a mass-losing AGB star and a hot, accreting post-AGB or White Dwarf companion. We propose to obtain FORCAST photometric and spectroscopic observations of eight symbiotic Miras, and six non-symbiotic AGB stars as a control sample, all of which have been observed by the International Space Observatory (ISO) and whose mid-infrared spectra exhibit the 10mu-m and 18mu-m silicate features. By comparing the ISO and FORCAST data, we will be able to characterize the changes in the spectral shape of the silicate features. We will model the spectra using the publicly available codes DUSTY, and RADMC-3D in order to obtain the dust properties at both epochs of observation, and thereby determine the physical processes that cause the changes in the silicate emission. Symbiotic Miras as a class have not been very well studied, and our observations will significantly expand our knowledge of these fascinating systems that are known to undergo nova-like explosions, and may be the lower-mass analogues of systems that eventually explode as Type I-a supernovae. A comparison of the observed changes that occur in the symbiotic systems with those in the non-symbiotic stars in our sample will allow us to determine the effects of the binary interaction on the evolution of silicate dust.

Proposal ID: 09_0052

Principal Investigator: Brandon Marshall (University of Nebraska at Kearney)

Title: Searching for Herbig Oe stars in the Mid Infrared

Abstract: Models suggest that during the formation process of massive stars the still accreting protostar generates enough radiation pressure to halt or even reverse spherically symmetric collapse directly onto the protostar when it reaches masses of 8-10 M. The leading theory for how these protostars can continue gaining mass is through accretion viaa circumstellar disk feeding mass onto the star. The timescales for disk destruction by a high-mass star indicate that the inner/warm disk survives much longer than the outer/cool disk, suggesting that we are much more likely to detect a remnant disk in the infrared rather than the submm. By finding signs of a remnant disk around recently formed massive stars we hope to show that some Oe-type stars are better thought of as "Herbig" Oe stars, analogous to lower-mass Herbig AeBe type stars, where the emission is associated with a remnant accretion disk rather than circumstellar material associated with mass loss. We will obtain MIR observations of late O-type stars to confirm whether these young massive stars do harbor a remnant accretion disk. Further observations should be able to detect the warm remnant disk by observing excess MIR emission, where current observations have not had the resolution to accurately distinguish stellar and nebular emission at longer MIR wavelengths. With MIR data from SOFIA along with optical and IR spectra we can more accurately model the circumstellar environment. We will use the FORCAST to obtain MIR photometry. FORCAST has higher resolution than WISE and also has wavelength coverage extending further into the infrared. This will allow us to build more accurate and extensive spectral energy distributions (SEDs) for comparison with models. Data taken will be used to build more complete SEDs in the MIR for the sample of stars to compliment stellar spectra taken with Gemini, DAO, WIRO. The project has the potential to improve our understanding of early stages of star formation and the evolution of high-mass stellar accretion disks.

Proposal ID: 09_0053

Principal Investigator: Jochen Eislöffel (Thüringer Landessternwarte)

Title: Catching the next bright accretion burst from a YSO on the rise

Abstract: Low-mass stars form via circumstellar disks through which matter is accreted onto the protostar. In recent years, it has become clear that this process is episodic and highly variable and -- occasionally -- leads to strong accretion bursts (so-called EXor or FUor outbursts), which may be caused by various mechanisms. The recently (by our team) discovered accretion burst in the high-mass young stellar object S255IR NIRS3 (HMYSO; M > 8 M_sun, L_bol > 5x10^3 L_sun) and the almost contemporaneous one associated with NGC6334I-MM1 indicate that HMYSOs experience disk accretion as well, and identify disk-accretion as the primary mechanism of star formation across the entire stellar mass spectrum. Of utmost interest for our understanding of this process and its consequences is now to find out which parts of the disk are affected by the outburst and on which timescales, and how this may vary with mass of the protostar. Here we are requesting Target-of-Opportunity observations for the next bright accretion burst in a YSO with FORCAST and FIFI-LS/HAWC+ observations (1h/45min each) while the outburst is on its rise, and a follow-up a few months later, to follow the spectral changes due to the burst energy propagation into the circumstellar environment. With these and archival pre-burst data we will derive the spectral energy distributions of the source. This constitutes an excellent dataset to learn more about where in the circumstellar disk such a burst starts, how it is triggered, and what its implications for planet formation may be.

Proposal ID: 09_0054

Principal Investigator: David Chuss (Villanova University)

Title: A Two-Color Polarimetric Survey of the Galactic Center

Abstract: We propose a Legacy program to utilize HAWC+ to map the central region of the Galaxy at both 214 µm and 89 µm. We will utilize the shared-risk scan mode polarimetry observing strategy. The 214 µm map is proposed as a test case because the total integration time is modest. Upon successful completion of the 214 map, (and the approval of the Cycle 9 TAC), we will proceed with the 89 µm survey in the second year of the program. The resulting data products will yield a transformative data set for understanding the magnetic fields in both the cool dust ring in the central 200 pc and the warmer dust component and its relationship to the hot features of the Galactic center. Such a data set would elicidate the role of the magnetic field in Galactic center dynamics from the 200 pc scale down to scales below a parsec.

Proposal ID: 09_0055

Principal Investigator: Omnarayani Nayak (Space Telescope Science Institute)

Title: Studying Gas Heating Mechanisms of a Super Star Cluster with SOFIA

Abstract: The N79 South giant molecular cloud (GMC) harbors one of the highest densities of embedded massive young stellar objects (YSOs) in the Large Magellanic Cloud (LMC). However the exact formation mechanism of the YSOs, which depend on how the parental gas is being heated and cooled, remains a mystery. At the heart of N79 South lies the embedded super star cluster (SSC) candidate H72.97-69.39. We propose to investigate H72.97-69.39 by analyzing the emission of the [OI] 63 μm and [OI] 145 µm lines in the N79 South GMC that is host to the SSC candidate. Whether mechanical heating from shocks or radiative heating from PDRs plays a more dominant role has long been debated. We will determine if [OI] 63 µm and [OI] 145 µm lines are in agreement with our predictions using PDR modeling, or if the presence of shocks is necessary to explain the fluxes we measure with SOFIA/GREAT Cycle 9 observations. With SOFIA/GREAT Cycle 9 observations of [OI] 63 µm and [OI] 145 µm lines, we will shed light on which of the two heating mechanisms plays a more important role in early-stage star formation. JWST GTO observations will give us a census of YSOs in the H72.97-69.39 region down to 1 M⊙. SOFIA/GREAT Cycle 9 observations will provide crucial and complementary information on the nature of the parental gas in which YSOs are forming.

Proposal ID: 09_0057

Principal Investigator: Margaret McAdam (NASA Ames Research Center)

Title: (16) Psyche: Confirming and quantifying the detections of the rotational heterogeneity hydrated minerals and/or pyroxene with SOFIA+FORCAST

Abstract: Asteroid (16) Psyche is a complex object that has been theorized to be a metallic world. More recent observations have identified the presence of rotational heterogeneity, a fine-grained regolith, pyroxene and hydrated minerals on its surface. As the target asteroid of the Psyche Mission, understanding this complex body is of great interest to the small bodies community. We propose to obtain rotationally resolved mid-infrared spectroscopy of (16) Psyche using SOFIA+FORCAST to quantify the composition of Psyche's equatorial region, to investigate the composition of the mass-deficit region and determine the distribution of regolith over the surface. The mid-infrared spectral region, covered by FORCAST, contains distinct spectral absorption features that can quantify the amount of hydrated minerals and the composition of pyroxene. Additionally, thermophysical modeling can be used to determine the thermal inertia over Psyche's northern mid-latitude region which can indicate the presence of regolith on its surface. The observations may help constrain Psyche's impact history by identifying the composition of impactors bringing exogenic material to its surface, or potentially the nature of Psyche's lost mantle material if pyroxene is identified. SOFIA is currently the only facility capable of observing asteroids using Q-band spectroscopy and is thus essential for understanding Psyche in preparation of the Psyche Mission.

Proposal ID: 09_0059

Principal Investigator: Dominik Riechers (Cornell University)

Title: [CII] Emission from the Most Luminous Galaxies in the Visible Universe at z>2

Abstract: Studies of far-infrared fine structure lines are the backbone to our understanding of interstellar medium (ISM) properties in galaxies throughout cosmic history, now reaching all the way back to redshifts beyond 9. The [CII] 158 µm line traditionally is the "workhorse" line among them, and has now been detected in hundreds of galaxies. Unfortunately it cannot be observed from the ground across most of the critical z=2–3 redshift range, when the history of cosmic star formation peaked. This has led to the dissatisfying situation where the brightest starburst galaxies in the universe across the entire sky, only discovered after the demise of Herschel, are currently lacking [CII] detections, causing a gap in our knowledge on these otherwise exceptionally well-studied systems. We here propose to demonstrate that, with the 4GREAT instrument, SOFIA is now ready to address this unfortunate gap, and the only current observatory able to do so. Targeting the three apparently brightest (strongly lensed) starburst-powered galaxies in the sky, found at redshifts 2.0, 2.2, and 2.6, we will obtain the first detections of ISM lines at high redshift with SOFIA. This exploratory study will open up an entirely new area of research for SOFIA by spectroscopically probing the early universe, reaching beyond what even Herschel was able to achieve in terms of spectral resolution.

Proposal ID: 09_0065

Principal Investigator: Archana Soam (SOFIA)

Title: Investigation on the interplay between gas and magnetic fields from large to small spatial scales in the IRDC G035.39-00.33

Abstract: The magnetic field (B-field) plays a crucial role in shaping molecular cloud structure within nearby star forming regions. However, its effect on structure formation is less clear when considering high-mass star forming regions outside our immediate neighborhood. Currently, observations that probe the magnetic field exist for only a few such high-mass star-forming regions (infrared dark clouds, IRDCs). In this project, we want to study the magnetic field morphology and strength in IRDC G035.39-00.33 (G35 hereafter) using SOFIA/HAWC+ observations. In existing gas kinematic studies, it is found that the filamentary structure of this cloud is a result of cloud-cloud collision. Dust polarization observations in 850um suggests that magnetic fields are important in the cloud-cloud collision process and formation of G35 but these findings are limited to cold denser regions only. We need to investigate what is happening on larger scales. How important are magnetic fields in the warm regions of the filament? Are B-Fields funneling material and guiding the cloud-cloud collision at all scales thus helping in formation of cloud structures? These questions can certainly be addressed when we have magnetic field over a wide range of spatial scales. Only HAWC+ can provide hints on this unexplored part of the puzzle in this cloud. From existing gas kinematics of C18O (1-0), 13CO (1-0), HCO+, H13CO+, CCS, HC3N from TRAO and Korean VLBI and NH3 (1,1) from GBT and dust polarization observations of G35, it was also found that the main filament (FM) will be gravitationally unstable if it is only supported by thermal pressure and turbulence. The estimation of the magnetic field strength from dust polarization observations is required for investigating the energy budget of the filament. In addition to the above, the proposed observations will be used for checking the stability of main filament F_M analyzing turbulence and magnetic fields against gravitational collapse.

Proposal ID: 09_0066

Principal Investigator: André Beck (Deutsches SOFIA Insitut)

Title: Disentangling Excitation Conditions in the Outflow of NGC 253

Abstract: We propose to observe the southeastern outflow of the starburst galaxy NGC 253 in [OIII] 52µm and 88µm line emission. The ratio of theses two lines is a direct measure of the electron- and thus H+ density in the observed region (Osterbrock & Ferland 2005). Recent observations of M82 with FIFI-LS show that, in contrast to current assumptions (e.g. Contursi et al. 2013, Fischer et al. 2010), gas in galactic outflows consists not only of neutral atomic and molecular gas, but also to a large fraction of ionized gas with H+ densities of ~200cm^-3 (C. Fischer in prep.). With the proposed observations we want to investigate gas density of the ionized gas component in galactic outflows. Furthermore, we want to analyze which mechanisms are responsible for gas excitation in these outflows. To do so, we will use the [OI] 145µm emission (which can be simultaneously be observed), as well as photometric data from Spitzer/IRAC, Spitzer/MIPS and Herschel/PACS (all photometric bands from 3.6 to 160µm) and [CII] line emission from SOFIA/FIFI-LS. With this wealth of data we will use the spectral synthesis code "Cloudy" (Ferland et al. 2017) which predicts emission from a molecular cloud of given parameters (e.g. metallicity, gas density, ...) heated by a source of given variables (e.g. spectral shape, intensity, ...). Comparing predictions from the code with our proposed and observed data will help us to disentangle which processes are responsible for gas excitation in galactic outflows, and whether shock excitation has to be taken into account.

Proposal ID: 09_0067

Principal Investigator: Terry Jones (University of Minnesota)

Title: Exploring the Magnetic Field Geometry in NGC 891

Abstract: We propose to explore the magnetic field geometry in the edge-on galaxy NGC 891 using SOFIA HAWC+ in polarimetry mode at 154 microns. HAWC+ measures the polarized emission of warm dust, not cosmic ray electrons as in radio observations and does not suffer Faraday effects nor the scattering effects that can plague optical and NIR observations. By mapping the magnetic field geometry in an edge-on galaxy, we will explore the presence of magnetic fields which are perpendicular to the galactic plane in the halo and the effect of dynamic processes in the galaxy on the magnetic field geometry in both the disk and the halo. While the effect of galactic feedback on magnetic fields has been considered in numerical models, the observational evidence is insufficient for any comparison. Our proposed studies will facilitate a deeper understanding on how magnetic fields off a galactic plane evolve and how galactic feedback affects magnetic fields in the halo.

Proposal ID: 09_0070

Principal Investigator: Sylvain Veilleux (University of Maryland College Park)

Title: The Bolometric Luminosities of Two Heavily Reddened Wind-Dominated Quasars Targeted in a JWST ERS Program

Abstract: Quasar activity almost certainly impacts the evolution of massive galaxies but the details are still uncertain. JWST Early Release Science program #1335 entitled "Q-3D: Imaging Spectroscopy of Quasar Hosts with JWST Analyzed with a Powerful New PSF Decomposition and Spectral Analysis Package" will address this question by mapping the spectacular large-scale winds in three red and obscured quasars covering a wide range of cosmic times from redshifts z = 0.4 to 2.9. The JWST data will allow for the first time to map the stellar component, multi-phase gas, and dust emission of distant quasar hosts all at once. However, a major weakness of this program is that the bolometric luminosities of two of the three targets are poorly constrained. This quantity has been shown in recent years to be the single most reliable predictor of the outflow energetics, perhaps an indication that radiation pressure is the main driving force behind these large-scale quasar winds although this explanation is not unique. The spectral energy distributions (SEDs) are expected to peak in the far-infrared (FIR), but photometry at these wavelengths is lacking. The proposed HAWC+ FIR observations on these two quasars will capture the flux near the expected SED peak, and thus reduce the uncertainties on the bolometric luminosity of each quasar by factors of 2-3. The revised luminosities will be combined with existing ground-based outflow dynamical measurements to determine where these two objects fit along the trends between outflow energetics and AGN luminosities seen in other less extreme systems, and whether an additional force other than radiation pressure (e.g., thermal, cosmic ray, and jet ram pressures) is needed to explain these more powerful outflows. This analysis will be revisited once the JWST data become available.

Proposal ID: 09_0072

Principal Investigator: Alexander Tielens (University of Maryland College Park)

Title: EXES Survey of the Molecular Inventory of Hot Cores

Abstract: The formation of massive stars is not well understood but accretion through a circumstellar disk is considered to be key. Properties of such disks are difficult to determine at sub-mm wavelengths, as beam dilution hampers observations of small (20 - 100 mas) scales and bright emission from the warm environment swamps the disk signal. The mid-IR dust continuum originates from the disk photosphere and absorption line studies directly probe the properties of warm, dense gas in those regions. Therefore, high spectral resolution, pencil beam absorption line studies at mid-IR wavelengths provide critical and unique diagnostics of these disks. We propose to use EXES on SOFIA for a high signal-to-noise (S/N~100) and high spectral resolution (R=50,000) survey of the 5.4–8μm region of the circumstellar disks associated with the protostar NGC 7538 IRS 1 and the protostellar binary W3 IRS 5. These data are complemented by L, M and N band surveys from the ground at comparable spectral resolution for complete 3–13μm spectra. Existing data in small spectral windows give confidence that we will detect hundreds of absorption lines from H2O, C2H2, CH4, HCN, NH3, and CS. Peak velocities can unravel the components associated with each of the binary components in W3 IRS 5. Line profiles are a measure of the (relative) distribution of these species in the disks. These lines can be analyzed using rotation diagrams and curve-of-growth techniques to derive excitation temperatures and abundances. Several of these species cannot be observed at sub-mm wavelength because they lack permanent dipole moments and/or telluric absorption. These species are key to understand the organic inventory and chemical processes relevant in dense (10E8–10E10 cm-3), warm (600 K) gas, such as the inner disks around massive protostars and the terrestrial planet formation zone in the solar nebula.

Proposal ID: 09_0073

Principal Investigator: Rebeca Aladro (MPIfR)

Title: Atomic and molecular gas in NGC 4945: Relative abundances distribution and kinematics in the galaxy

Abstract: We propose to map the [CII] emission in the central kiloparsec of the galaxy NGC4945 with high spectral resolution for the first time. Our goal is to study the properties of the ionised atomic gas in the different morphological and kinematical components of the galaxy (bar, rotating disk, and spiral arms). We will investigate the effects of self-absorption/continuum absorption and opacity on the [CII] emission, which are important to understand the origin of the [CII] deficit with respect to the infrared luminosity in this galaxy (and in (ultra) luminous infrared galaxies). This is a combined SOFIA, ALMA, and APEX project. The [CII] data will be compared to the neutral carbon [CI] (APEX) and CO (ALMA) maps of the same region of NGC4945. The combination of the (ionised and neutral) atomic and molecular gas will constitute the most detailed study of the life cycle of the inter-stellar medium and star formation in this galaxy. We will also compare the results to the recently completed SOFIA/GREAT [CII] maps toward the Central Molecular Zone (CMZ) of the Milky Way and toward Orion. The comparison with the CMZ will highlight how the different star formation rates of the two galaxies impact the [CII] properties, while the Orion map will be taken as a template of a photon-dominated region, similar to what is found in the central starburst disk of NGC4945.

Proposal ID: 09_0076

Principal Investigator: Alberto Bolatto (University of Maryland College Park)

Title: SOFIA GREAT Mapping of the LMC Northern Molecular Ridge

Abstract: We propose GREAT [CII] mapping of an area of 12' x 24' (170pc x 350pc at 5pc resolution) of the Northern Molecular Ridge in the LMC, located just South of 30 Doradus, matching the coverage of existing ALMA CO 2-1 observations. The Northern Ridge contains progressively younger star forming regions in the North to South direction, likely triggered by large scale flows of material, and it constitutes a prime laboratory to study the processes that create and regulate massive star formation in galaxies. The data will allow us to determine the mass, kinematics, and structure of the neutral (atomic and molecular) gas in this region, and quantify the effects of radiative feedback, stellar winds, and HII region expansion on the parent clouds. A small fraction of this area has been mapped by SOFIA, and although the existing maps provide tantalizing hints and allow us to secure [CII] intensity estimates, they do not have the sensitivity or the coverage to accomplish our target science. We outline 6 publications on topics ranging from large scale flows and feedback to the formation of CO-bright gas and cloud properties that would result from the combined analysis of these datasets.

Proposal ID: 09_0077

Principal Investigator: Eric Omelian (Space Science Institute)

Title: Monitoring the Eclipse and Periastron Passage of the Symbiotic Mira R Aqr

Abstract: R Aqr is a nearby symbiotic system consisting of a dusty, oxygen-rich Mira variable and a hot accreting White Dwarf (WD). It contains a spectacular jet, which is fueled by the accretion flow onto the WD. Surrounding the central system are two extended shells that are the remnants of nova-like outbursts that happened several hundred years ago. The orbital period of the system is about 44 years, and the periastron passage happens during an extended 8 year "eclipse" when the accreting WD passes in front of its AGB companion. These episodes are associated with a steep drop in the visual magnitude of the AGB, and with enhanced jet activity. R Aqr has just entered its much anticipated once-in-44-year eclipse. The brightness of the prominent silicate features at 10 and 18 mu-m, after having dropped by a factor of two between 1996 and 2017 (Omelian et al. 2020) appear to be rising again. We propose to obtain FORCAST photometry and grism spectra, which will allow us to characterize the changes in the strength and shape of the silicate features during this highly active phase in the binary system. We will use a 3D radiative transfer code to model the emission, and thereby constrain the density and temperature distribution in the dust shell. We will explore the effects of departures from spherical symmetry, which are expected and have been imaged in such accreting systems (e.g., Bujarrabal et al. 2018).

Proposal ID: 09_0078

Principal Investigator: Miguel Angel Requena Torres (University of Maryland Baltimore County)

Title: Nitrogen chemistry in the Galactic Center: chasing the formation of hydroxylamine an RNA precursor

Abstract: Spectral surveys at millimeter wavelengths toward Giant Molecular Clouds in the Galactic Center have revealed that these clouds represent one of the main reservoirs of complex organic molecules in our Galaxy. In previous works, it has been established the inventory of O-bearing and N-bearing COMs, and have revealed the presence of many prebiotic molecules. One of them is hydroxylamine (NH2OH), a key precursor of pyrimidine and purine RNA ribonucleotides within the primordial RNA chemical scenario for the origin of life. Despite exhaustive searches across different environments in the ISM, NH2OH has been detected only toward the quiescent Galactic Center GMC G+0.693. Little is known about the formation routes of this molecule. Either on grain surfaces or in the gas phase, they involve the amine species NH, NH2 and NH3, whose low energy transitions have not been observed before toward this source. We will carry out observations of several lines of NH2 and NH3 using GREAT to constrain the molecular abundances of these amine species and thus, to provide constraints to the formation processes of NH2OH. For completeness, our observations will also cover several transitions of NH. The inferred observations will be key for constraining the chemistry of the amine species NH, NH2 and NH3, which will help us to complete the nitrogen chemistry puzzle and to understand the role of amine radicals in the formation of prebiotic molecules such as NH2OH.

Proposal ID: 09_0079

Principal Investigator: Christian Fischer (DSI)

Title: Photo-dissociation and shocks in DR21 (OH)

Abstract: Context Massive star formation is a very energetic process. How the energy injected by the young massive stars affects the parental molecular clouds is of importance for star-forming theories and galaxy evolution. Aims This proposal aims at studying radiative and mechanical feedback from DR21(OH). The ionized interface of photo-dissociation regions (PDRs), where radiative processes erode the cloud, is especially the target of the proposed investigation. Possible contribution of shocks irradiated by UV photons will be also identified. Methods FIFI-LS has already gathered data in the DR21 region, but for a full analysis the [OIII] lines and additional CO lines are needed for DR21(OH). With the proposed observations of the [OIII] lines and two high-J CO lines, the data set will be complete and modeling can provide spatial information on physical properties e.g., temperature, densities, shocks and UV radiation fields of the PDR and the ionized regions. Synergies This study is complementary to the FEEDBACK Legacy proposal which will provide high spectral resolution maps of the Cygnus X region to study the effects of winds on the star-forming regions with upGREAT, whereas the FIFI-LS observations provide the diagnostic lines suitable for a PDR and shock analysis. The data will be also complementary to PACS single footprint maps, which lack sufficient spatial information on line emission.

Proposal ID: 09_0081

Principal Investigator: Conor Nixon (NASA Goddard Space Flight Center)

Title: A Search for Complex Molecules in Titan’s Atmosphere

Abstract: We propose to attempt first detections of three previously unseen molecules in Titan's atmosphere. These include one cyclic/aromatic molecule (pyridine) and two heavy linear/aliphatic molecules (C6H2, C4N2). Our proposed investigation utilizes SOFIA's unique ability to access the far infrared spectrum exhibited by Titan's cold atmosphere, with all of our target species at 16-25 microns, a region that has poor transmission for ground-based spectrometers (e.g. IRTF/TEXES). This far-infrared spectral region exhibits low-energy C-H bending modes for both linear and cyclic molecules that are ideal for making unique structural identifications. Confirmation of these molecules is of high scientific significance, since Cassini mass spectra have indicated hints of their existence in Titan's ionosphere. Moreover, nitrogen-heterocyclic molecules such as pyridine have high astrobiological importance due to their similarity to backbone rings of DNA nucleobases. Detection of these molecules will help to elucidate the chemical pathways that connect from the plethora of small molecules currently identified in Titan's neutral atmosphere and provide constraints for photochemical models.

Proposal ID: 09_0083

Principal Investigator: Gavin Rowell (University of Adelaide)

Title: Deep C+ Studies of the Brightest Gamma-Ray Supernova Remnant RXJ1713.7 − 3946

Abstract: In this SOFIA propose we aim to use the THz-frequency fine structure line of ionised carbon, C+, to further trace the "dark" component of the ISM gas associated with the brightest-known TeV gamma-ray supernova remnant (SNR). Our target is the young SNR RXJ1713.7-3946 which still harbours the bulk of its sub-TeV cosmic-ray particles. The high cosmic-ray density inside the SNR bubble, about 4000 times higher than the Galactic average, could lead to significantly enhanced C+ abundance though ionisation of the neutral gas. This is a follow up to a previous project where we successfully detect C+ albeit with average large regions together. In this proposal we aim to increase the signal to noise using the raster map observing mode as opposed to the OTF mapping mode we used previously. We plan to map several parts of the SNR rim with the SOFIA upGREAT instrument that will allow us to look for variations in C+ across the SNR shock and regions with localised dense molecular and atomic gas. We will combine our map of C+ with new CO images at similar resolution to create the most detailed inventory of the total molecular column so far. Comparing this to the new TeV gamma-ray image from H.E.S.S., we can then finally start to quantify the level of cosmic-ray acceleration occurring in this prominent SNR, the brightest of its type in gamma-ray astronomy, and thus help to advance our understanding of where Galactic cosmic-rays come from. In addition, our study will provide a new opportunities to follow the chemical production channels for C+, and its dynamics in a region under the influence of a very fast (>1000 km/s) and young (~1000 yr) SNR shock that has entered dense molecular and atomic gas regions.

Proposal ID: 09_0084

Principal Investigator: Robert Brunngraeber (University of Kiel)

Title: Self-scattering in the protoplanetary disk of HL Tau with SOFIA

Abstract: Recent observations at (sub-)mm wavelengths suggest that scattering of thermal re-emission ("self-scattering") by large dust grains is the dominating contributor to the observed polarisation of protoplanetary disks (e.g. Hull et al. 2018, Lee et al. 2018, Ohashi & Kataoka 2019). In order to disentangle polarisation due to emission by magnetically aligned grains from scattering, multi-wavelength observations are mandatory. Furthermore, the scattering properties are strongly wavelength-dependent and thus -- in combination with radiative transfer simulations -- such observations are essential to put stringent constraints on the dust composition and grain size distribution (Brunngräber & Wolf 2019). Our goal is to evaluate the contribution of emission by aligned grains vs. scattering, and provide unique insights into the dust phase of a well-selected protoplanetary disk by combining SOFIA observations with archival polarimetric observations of ALMA. For this purpose, we propose to observe HL Tau with HAWC+ in four wavelength bands in the far-infrared (FIR). We will make use of polarimetric observations in the wavelength bands A, C, D, and E to obtain the orientation and degree of linear polarisation of HL Tau. These observations of a protoplanetary disk in the FIR wavelength regime will close the gap between the mid-infrared and (sub-)mm wavelength range. We will obtain the Stokes parameters I, Q, and U of HL Tau to provide one of the first detections of polarisation of a protoplanetary disk in the FIR. Together with the already obtained polarimetric data at 870 µm, the wavelength-dependency of the polarisation degree and orientation can be estimated. Based on this, it will be possible to constrain the origin of the polarisation in the FIR, whether it is due to scattering, as observed with ALMA, or due to aligned dust grains. Furthermore, the grain size distribution and chemical composition of the dust will be constrained.

Proposal ID: 09_0085

Principal Investigator: Jonathan Tan (University of Virginia)

Title: SOFIA Massive (SOMA) Star Formation Survey - High Priority Protostars for Survey Completion

Abstract: The SOMA Survey is a multi-cycle project to build a large, high legacy value sample of high- and intermediate-mass protostars that are uniformly observed across MIR and FIR bands to test theoretical models of massive star formation. Here, especially given that this may be the last cycle in which FORCAST is available, it is proposed to observe 10 high priority massive protostars with this instrument via this Regular Program proposal. This will result in effective completion of the survey. Source selection here is driven by the desire to have good sampling of all evolutionary and environmental types. Especially the unique 37 micron imaging reveals thermal emission from outflow cavities and the relative fluxes from the near and far-facing sides probes the amount of dense gas in the immediate vicinity of the protostar. Core Accretion models generally involve larger quantities of such gas than Competitive Accretion models. Observational results will be compared against specific predictions of a suite of radiative transfer simulations to make quantitative tests of the models.

Proposal ID: 09_0088

Principal Investigator: Karl Menten (Max Planck Institute for Radio Astronomy; Bonn)

Title: The aftermath of a stellar collision in the Galactic Bulge

Abstract: We propose to observe BLG-360, which belongs to a rare class of transients known as red novae. Their eruptions are stellar-merger events which provide us with an unprecedented opportunity to study the most catastrophic form of binary interaction between non-compact stars. Red-nova studies are expected to shed a new light on the problem of the common-envelope evolution, which is central to modern stellar astrophysics, but which has been eluding theoreticians for decades. We propose to obtain wide-range photometric measurements with HAWC+ and FORCAST that will allow us to reconstruct the full spectral energy distribution (SED) of BLG-360, the least studied of the five known Galactic red-nova remnants. The SOFIA data will be complemented by millimeter-wave observations at the Submillimeter Array (SMA). The SED, analyzed employing state-of-the-art radiative-transfer modeling, will constrain the remnant geometrical structure, physical state (temperatures, mass, densities), and chemical composition (dust mineralogy). These are crucial to identify the type of stars that merged in BLG-360 and point toward the mechanism that triggered the common envelope phase and the subsequent merger. This SOFIA study will complete our aim to fully characterize the entire Galactic sample of the post-outburst remnants of red novae. We suspect that BLG 360, as the slowest red nova, is also the most dusty one with dust mass of approximately 2.5 solar masses, larger than expected to be produced in any supernova. Because the remnant is very red and dusty, it disappeared from optical to near-infrared wavelengths and currently SOFIA is the only telescope capable of studying it. SOFIA is also the only facility that can deliver the nearly simultaneous set of broadband observations required for our advanced radiative-transfer modeling.

Proposal ID: 09_0089

Principal Investigator: Jonathan Tan (University of Virginia)

Title: The Inception of Star Cluster Formation: [CII] Emission from IRDCs Massive Protoclusters and GMC Collisions

Abstract: Most stars are born in clusters. Thus, the processes that may initiate star cluster formation are of fundamental importance throughout astrophysics, from the evolution of stellar populations in galaxies to the formation of planets in protoplanetary disks in these environments. Infrared Dark Clouds (IRDCs) are now recognized as the likely precursors of star clusters. Thus it is important to understand the kinematics, dynamics & formation environments of IRDCs. We propose to utilize the efficient OTF mapping capabilities of upGREAT to map [CII] and [OI] emission in a sample of 3 IRDCs that have been extremely well studied over the last decade with numerous facilities, including Spitzer, IRAM 30m, IRAM PdBI, Herschel, Chandra & ALMA. [CII] probes the photodissociation region around the IRDC. Thus it provides crucial information on the kinematics of the gas that is becoming molecular and joining the IRDC. Different theoretical models of IRDC formation are expected to have different signatures of [CII] kinematics. For example, simulations of dense gas formation via either decaying turbulence or triggering by cloud-cloud collisions make specific distinguishing predictions for [CII] spatial and kinematic structures. These will be tested against upGREAT observations to deduce the processes that initiate star cluster formation. We also request GBT-ARGUS time to map 13CO(1-0) and C18O(1-0) at high angular and velocity resolution to obtain the best maps of molecular gas kinematics to compare to those of [CII] and further test models of IRDC dynamics and formation.

Proposal ID: 09_0092

Principal Investigator: Rebecca Pitts (Niels Bohr Institute; University of Copenhagen)

Title: Neutral Atomic Sulfur in Cygnus-X: Key to the Missing Sulfur Problem?

Abstract: Context. Sulfur is the tenth most abundant element in the universe, and S-bearing species are both eminent shock tracers and -- in the case of organosulfur compounds -- important prebiotics. However, in dense molecular cores, detectable S-bearing species can account for as little as 0.1% of the sulfur budget. This severely limits our ability to use S-bearing species to say anything quantitative about the gas it traces. Neutral atomic sulfur is not well-explored as an alternative sink because the 25.25 µm [SI] fine structure line is hard to observe. Aims. With SOFIA-FORCAST, we seek to confirm the detectability of the 25.25 µm [SI] line from five sources in Cygnus-X that also have their S-bearing molecular content well-accounted for through observations with the SubMillimeter Array (SMA). With the proposed observations, we intend to make a combined study of the atomic and molecular sulfur budget toward these protostars to shed new light on sulfur reservoirs around protostellar cores. Methods. We target the [SI] line with FORCAST primarily to confirm detection toward Cygnus-X sources. The measured fluxes will then be compared to emission from S-bearing molecules. To estimate the amount of atomic sulfur, we will compare observations to sophisticated shock models currently in development. Lastly, the combined atomic and molecular sulfur data will be compared to state-of-the-art lab experiments where physical and chemical conditions are simulated. Synergies. These data compliment SMA observations of the same objects as traced by a variety of S-bearing and other molecular species. Furthermore, as shown above, the proposed program share synergies with lab experiments and shock modeling. Lastly, we intend for this to be a pilot for resolved observations of the same lines with EXES. Anticipated Results. With this unprecedented survey of S-bearing species, atomic and molecular, toward a significant sample of protostars located in a single cloud, we expect to make substantial headway in determining the total sulfur budget toward star-forming regions. The results will also inform new laboratory experiments being carried out by our team.

Proposal ID: 09_0093

Principal Investigator: Jens Kauffmann (Haystack Observatory; Massachusetts Institute of Technology)

Title: Tracing cosmic star-forming Gas: Connecting Cii HCN and other Species in the LEGO Survey

Abstract: We wish to examine whether the millimeter-wave emission of HCN correlates with the emission of [CII] as probed by SOFIA. We will do so by mapping [CII] in a representative sample of molecular clouds which have been observed in HCN as part of the LEGO Large Program on the IRAM 30m-telescope. This experiment is of fundamental importance for progress in extragalactic star formation research, as it is needed to reliably interpret the so-called Gao & Solomon relation. Specifically, this project examines whether HCN can serve as a reliable tracer of dense gas (i.e., densities >10^4 cm^–3) in other galaxies, or whether the excitation of HCN is to a significant extent influenced by the electrons released during the formation of [CII]. Excitation by electrons would enable bright HCN emission in gas of low density, fundamentally changing the interpretation of HCN emission as a central tool for the study of galaxies. The LEGO sample is unique in that it systematically explores molecular line emission between 85 and 115 GHz in a sample of molecular clouds that is representative of the Milky Way, i.e., ranging from the inner Galaxy to the outer disk. Collaboration with the LEGO team now provides us with unprecedented wide-field views of many critical molecular species, such as HCN, CS, and N2H+. We have now used this sample to systematically identify a subset of molecular clouds with remarkable trends in HCN emission. We now wish to obtain [CII] maps, as such data are critical for the interpretation of existing LEGO data. A secondary goal is to use the new [CII] maps -- which will be among the largest and most sensitive maps taken so far -- to better explore the nature of [CII] emission in molecular clouds. Specifically, we can examine how [CII] emission depends on the physical conditions revealed by the 10-15 emission lines imaged by the LEGO survey. This aids future work with SOFIA on [CII] emission by any investigator.

Proposal ID: 09_0094

Principal Investigator: Lee Armus (Caltech)

Title: SOFIA Observations of the Galactic Wind in NGC 1365

Abstract: Galactic-scale winds, driven by the collective effect of massive stars and supernovae, have been invoked as a source for the heating and metal-enrichment of both the intra-cluster and inter-galactic medium, and as the source of the mass-metallicity relation for galaxies. Feedback from star formation and Active Galactic Nuclei (AGN) play a large, but poorly understood role in regulating the growth of galaxies over a wide range of mass scales and a large fraction of cosmic time. Here, we propose to obtain spatially resolved, far-infrared spectra with FIFI-LS on SOFIA, of the luminous infrared galaxy, NGC 1365, which is known to host a galactic superwind. FIFI-LS offers a unique opportunity to study the large scale, far-infrared line emission, via the [CII] and [OIII] fine-structure lines, associated with these winds, as they shock-heat and accelerate gas from the interstellar to the circum-galactic medium, providing robust estimates of the velocities, mass outflow rates, and ultimate fate of the wind material. With FIFI-LS, we can spatially resolve the properties of the outflowing ISM on sub-kpc scales in key FIR tracers that penetrate the dust, placing important constraints on models of feedback and quenching of star formation in galaxies, and providing a direct link to studies of high-z galactic outflows being discovered with ALMA. Our total request, including all overheads, is 3.2 hrs.

Proposal ID: 09_0096

Principal Investigator: Cristian Guevara (University of Cologne)

Title: [CI] observations in Feedback sources

Abstract: Young massive stars excite the ISM, creating expanding H II regions that carve into the surrounding molecular clouds forming spherical or ring-like structures. This interaction allows the creation of an intermediate region between the H II region and the molecular cloud, namely the photodissociation region (PDR). Here, ionized, atomic, and molecular material coexist, where ionized carbon emission peaks, followed by the atomic and CO-dark gas traced by atomic carbon. Given these conditions, the [CI] emission originates between the C + and CO layers, with an Av of ∼3 mag. Here, CI arises as an excellent tracer of the PDR molecular gas, acting as a complement to the CII, tracing material colder and denser than CII. Also, CI emission is proposed to trace CO dark H 2 gas, invisible to the CO molecular emission. Moreover, it has been suggested as a tracer for cloud-cloud collision and for the expansion of the cold and dense material outside the expanding HII regions. Hence, atomic carbon becomes the missing piece of the puzzle regarding the completeness of the full carbon budget and the tracing of the invisible material between the ionized and the dense molecular layers. We have selected three FEEDBACK sources for this proposal, NGC7538, RCW49, and W40, to observe fully sampled maps in CI (and several mid and high-J CO lines) using the 4GREAT instrument. These regions have been partially mapped in CII and the observations still continue. These regions are HII regions with active massive star formation and complex phenomena such as stellar winds, cloud collisions, and HII expansion. The study of these regions would allow us to understand better the CO dark H2 molecular gas and the gas dynamics, considering that the [CI] emission is the missing link between the ionized [CII] and the cold molecular CO gas.

Proposal ID: 09_0097

Principal Investigator: Seamus Clarke (I. Physikalisches Institut; University of Cologne)

Title: [CII] as a tracer of pre-shock and post-shock gas in a supernova remnant

Abstract: Fast supernova remnant (SNR) shocks emit high energy photons, and cosmic rays, which are absorbed by the pre-shock gas, altering its chemical and thermal properties. When the shock impacts regions of the dense ISM, the shocked gas is able to cool rapidly to produce a hot dense post-shock region, bright in atomic and ionic fine structure lines. We aim to observe the [CII] 157.7 micron line to probe the pre- and post-shock gas in parts of the X-ray luminous CTB 109 (G109.1-1.0). CTB 109 is associated with a giant molecular cloud (GMC) complex, making it a prime choice for studying the interaction of a SNR with dense ISM gas. With the large bandwidth and high velocity resolution of the upGREAT receiver we will be able to capture and resolve both the pre- and post-shock [CII] components. Combined with previous observations of CO, dust, X-rays and radio, the [CII] emission will allow us to probe the pre-shock gas, the shock layer, and the post-shock gas, giving an unprecedented picture of the gas covering the molecular, atomic and ionised phases of the ISM. A new radiative shock model being developed in Cologne which includes hydrodynamics, non-equilibrium chemistry, radiative transfer of UV and X-ray photons and non-equilibrium ionisation populations will allow us to self-consistently model the pre-shock and post-shock regimes and determine important shock properties such as its velocity, initial energy, age and the pre-shock density. We ask for 3.5 hours of total observing time to complete our mapping region.

Proposal ID: 09_0100

Principal Investigator: Giuliana Cosentino (Chalmers University of Technology)

Title: The Infrared Dark Cloud G034.77-00.55: Magnetic field in large scale shock interactions

Abstract: Observations with Spitzer and Herschel satellites have revealed that the Interstellar Medium (ISM) is organised in filamentary structures called Infrared Dark Clouds (IRDCs) hosting the earliest phases of massive stars and star clusters formation. Current theories of IRDCs formation suggest that large scale shock interactions triggered by stellar feedback can compress the atomic and molecular ISM gas, leading to the formation of IRDCs and initiating star formation within them. Recent studies have identified a large scale shock interaction triggered by a SNR toward the IRDC G034.77-00.55. The gas compression caused by the shock propagation toward the cloud enhances the post-shock gas density to values sufficient to initiate star formation. However, it remains to be addressed, from an observational point of view, how the shock affects magnetic field properties in the post-shocked gas. Hence, we propose to use the SOFIA instrument HAWC+ to investigate the magnetic field orientation in the IRDC G034.77-00.55 and its shock compressed region, with the aim to compare its morphology with that predicted by state of the art molecular cloud formation models. The obtained data will also be used to compare the shocked compressed gas distribution, probed my multiwavelength tracers, with the magnetic field orientation to test the shock wave potential to initiate star formation in the dense ISM.

Proposal ID: 09_0101

Principal Investigator: Giuliana Cosentino (Chalmers University of Technology)

Title: Large Scale Shock Interactions in Infrared Dark Clouds: tale of a forming cloud

Abstract: Observations with Spitzer and Herschel satellites have revealed the presence of massive and very infrared dark filaments across the Interstellar Medium (ISM), known as Infrared Dark Clouds (IRDCs). IRDCs are known to host the earliest phases of star formation in the Galaxy and the study of their formation is essential to infer the physical and chemical conditions necessary to initiate star formation within them. Among different formation theories, IRDCs have been proposed to be assembled by multiple shock episodes on the diffuse atomic medium of the ISM, triggered by the complex network of expanding galactic bubbles. Such interactions compress the diffuse material enabling its conversion from atomic into molecular, as a consequence of the gas cooling processes. Recent studies have analyzed the large scale shock triggered by the supernova remnant W44 on the nearby IRDC G034.77-00.55 and have estimated that the shock compression experienced by the post-shock gas enhances the gas density to values sufficient to initiate star formation. However, disturbances on the gas kinematics due to the shock have so far been investigated mainly using molecular tracer emission and it is thus missing any information on the atomic more diffuse gas from which the cloud may have been assembled. Hence, we propose to use the SOFIA instrument GREAT to map the C[II] emission across the IRDC G034.77-00.55 and its shock compressed layer. We aim to obtain a detailed picture of the C[II] kinematic structure and to qualitatively compare it with that predicted by state of the art molecular cloud formation models. The obtained data will allow us to investigate the shock potential to have formed/shaped the cloud and to initiate the star formation process within the source.

Proposal ID: 09_0103

Principal Investigator: Robert Simon (PH1)

Title: Origin of a Large Arc-like Structure at the Far Side of the X1 Cusped Orbit

Abstract: A large (~ 8 pc in radius) arc-like structure (hereinafter referred to as "HVG-Arc") of unknown origin was detected at the far side of the X1 cusped orbit towards the line of sight to the Sgr A Complex. The HVG-Arc is detected in submm [CI](1-0) and CO(4-3) observations by Garcí­a et al. (2016) and it is found at high positive radial velocities, between +170 to +190 km/s. Using the unique capabilities for [CII] mapping of the SOFIA Observatory, we aim to identify the nature of the excitation source(s) by investigating the line strength spatial variation of the [CII] emission originated by the interaction with either massive stars, SNRs, or due to large-scale turbulence. Mm and submm observations suggest a PDR origin of the emission, when compared with existing PDR and XDR models in Meijerink et al. (2006), but a definitive statement can not be made with our current data sets. Therefore [CII] SOFIA/upGREAT observations, tracing the FUV field originating possible from massive stars, are needed to reliable disentangle the nature of the observed emission. For this purpose, we have selected four positions across the HVG-Arc for study. If massive stars or SNRs are responsible for the observed emission at the HVG-Arc, it would imply that the formation of massive stars can take place also in X1 orbits, and it is not only restricted to be triggered by large-scale gas collisions at the X2/X1 orbits intersection (e.g. Sgr B2), or in compressed gas within X2 orbits (e.g. Sgr A Complex).

Proposal ID: 09_0104

Principal Investigator: Jonathan Tan (University of Virginia)

Title: Magnetic Fields at the Onset of Star Formation: Polarization Mapping of Infrared Dark Clouds

Abstract: Most stars are born in clusters, so the processes that initiate star cluster formation are of fundamental importance throughout astrophysics. Infrared Dark Clouds (IRDCs) are now recognized as the likely precursors of star clusters. Thus it is important to understand the physical processes that control IRDC formation and evolution. We propose to observe 214 micron polarized emission from dust in a sample of nine well-studied IRDCs. These clouds have been mapped extensively with many other facilities, including IRAM 30m and ALMA to study the kinematics of the molecular gas that reveals properties of the turbulent motions. However, the B-field morphology and strength in these IRDCs are currently very poorly explored, thus motivating this SOFIA-HAWC+ proposal. Polarized emission is expected to be well-detected in many independent positions over the clouds. Sophisticated numerical simulations of magnetized clouds will also be used to help interpret the observations. We also request GBT-Argus time to map 13CO(1-0) and C18O(1-0) at high angular and velocity resolution to obtain the highest spatial dynamic range maps of molecular gas kinematics. Analysis of these maps will yield independent estimates of B-field properties, which will be compared with those derived from the HAWC+ observations. This will provide important tests of the fidelity of polarized dust emission methods of magnetic field estimation. Using all these methods, this project will enable a much improved understanding of the importance of B-fields in IRDCs and thus for the onset of star cluster formation.

Proposal ID: 09_0107

Principal Investigator: Alexander Tielens (University of Maryland Baltimore County)

Title: Magnetic Fields and Massive Star Feedback

Abstract: Feedback through stellar winds drives the interaction of massive stars and their natal molecular clouds and is an important component of the evolution of the interstellar medium of galaxies. This interaction is mediated through interstellar magnetic fields. We propose to map the magnetic field topology of the stellar wind bubble (the Veil) blown by θ1 Ori C in Orion using HAWC+ in band C (89 μm). We will combine these results with archival, velocity resolved, upGREAT [CII] 1.9THz observations of this bubble that provide the kinematics and kinetics as well as the physical conditions of the gas in the Veil. We will compare the magnetic field topology with the bubble morphology and with the velocity gradients derived from the [CII] observations. We will determine the strength of the magnetic field with the Davis-Chandrasekhar-Fermi method. In addition, we will use second-order structure-function of polarization angle orientations to estimate the ratio of the turbulent to magnetic field energy. In this way, we will quantify the role of magnetic fields in channeling and constraining the mechanical energy input in regions of massive star formation.

Proposal ID: 09_0110

Principal Investigator: José Pablo Fonfría (IFF-CSIC)

Title: Searching for C4 in the C-rich AGB star Y CVn

Abstract: To date, more than 200 molecules have been found in different environments such as molecular clouds or circumstellar envelopes, some of them as large as C70. Molecules are involved in many physical processes that significantly affects the dynamical behavior and the evolution of large scale structures or systems as, e.g., the circumstellar envelopes of the Asymptotic Giant Branch stars (AGBs). The chemistry of these objects has been tried to be explained for a long time but only the formation routes of the most abundant molecules are really understood. It is of particular interest the chemical reactions involved in the growing of different molecules such as the carbon chains, Cn. Some members of this family have been detected in the C-rich AGB stars IRC+10216 and Y CVn, which display optically thick and thin envelopes, respectively. In particular, C2, C3 and C5 are in IRC+10216 with a medium to low abundance and C2 and C3 in Y CVn with a high abundance. The chemical models suggest that the column density of the members of this family decreases when the number of carbon atoms grow. This means that C4 is expected to be in the envelopes of both stars but it has not been observed in space so far. Several weak ro-vibrational lines are present in a survey of IRC+10216 carried out with EXES around 6.456um that could be lines of the C4 band nu3. However, the low number of lines along with the complexity of the spectral region hamper the identification. Y CVn is a much more suitable target to look for this molecule, considering the high abundance of the other member of its family. In order to explore the spectral range where these still unidentified lines were found and aiming to discover C4 in space, we propose to observe Y CVn around 6.456um with EXES in its High_Low configuration, a very good S/N ratio of 200, and a resolving power of than 85,000.

Proposal ID: 09_0113

Principal Investigator: Alejandro Serrano Borlaff (NASA Ames Research Center)

Title: Testing for multi-component magnetic fields and their effects on the structure of galactic disks

Abstract: The vast majority of spiral galaxies present breaks in their surface brightness profiles, but their wide range of morphologies makes extremely difficult to contrast the proposed evolutionary paths. Despite theoretical efforts, there is not yet a unique explanation for their formation. Magnetic fields have been proposed as possible hidden factor for the formation of galactic disks. These fields shape the cold molecular gas filaments while regulating star formation. They also drive gas inflows, affecting the ionized gas before star formation, enabling radial migration processes that can modify the final disk structure. Nevertheless, no previous study has ever compared the presence of galactic disk breaks with the far infrared (FIR) structure of the magnetic field in the molecular gas. Previous works are mainly based on radio observations, which trace the warm diffuse interstellar medium. Nevertheless, the star formation takes place at a different gas phase and location in the galaxy - the cold molecular disk - which is only observable in FIR. We propose to observe the spiral galaxy NGC4501 with HAWC+, to study its 154um polarization map. NGC4501 is currently in the first stages of ram pressure stripping and is the perfect experimental setup for the proposed studies. The outskirts of the radio polarization map are clearly distorted but its molecular gas disk remains undisturbed, decoupled from the warm HI disk. In addition, it presents an inner sharp break at 1' in its surface brightness profile, detectable with HAWC+. SOFIA/HAWC+ is the only existing platform in the world where this experiment can be done, integrating the required sensitivity, wavelength, and polarimetric capabilities for the observations. Combining this data with archive radio and FIR polarization maps we will disentangle the different components of the B-fields as a function of the multi-phase ISM and resolve if there is any relation between them and the disk structure.

Proposal ID: 09_0114

Principal Investigator: Uma Gorti (SETI Institute/NASA Ames)

Title: Tracing cool disk winds with the [OI] 63 micron line

Abstract: Accretion and accompanying winds and outflows drive the evolution of protoplanetary disk masses and dictate planet formation timescales, but the underlying physical processes are poorly understood. Current wind tracers can only probe ~ 5000-10000 K gas and may not be sensitive to radii where most of the mass loss occurs. Therefore, the relative importance of viscous accretion vs. disk winds/outflows is unknown and the efficiency of angular momentum extraction and disk lifetime estimates are uncertain by nearly an order of magnitude. The proposed project is a pilot study aimed at detecting and characterizing a possible cool component of a T Tauri disk wind. Our goal is to use the OI 63um line to detect a cool wind counterpart to the jet and hot wind seen in optical forbidden lines from the protoplanetary disk around AS 205N. If most of the mass loss occurs in a wind that is too cold to excite the optical lines, then current estimates of the mass loss rate will increase by an order of magnitude becoming close to the mass accretion rate, with implications for angular momentum transport efficiency in disks. The very high resolving power of GREAT can easily isolate the jet and wind components and establish the presence or absence of a cooler wind. We will use theoretical models to analyze and interpret the line profiles, and with available ancillary data determine the wind emitting region and mass loss rate.

Proposal ID: 09_0115

Principal Investigator: Michael Kaufman (San Jose State University)

Title: An upGREAT Map in M20: [OI] and [CII] Emission from a Young Star Forming Region

Abstract: Using upGREAT to map a region of strong [OI] 63μm and [CII] 158μm line emission in the Trifid Nebula (M20), and comparing our results with existing infrared continuum maps from Herschel and Spitzer, we will be able to study the physical conditions in this very young massive star forming region, which contains a well-defined, bright, edge-on PDR, a photoevaporating globule with an embedded protostar, several cometary globules, and protostellar jets. Using the velocity-resolved spectra, we will be able to measure the relative contributions of PDRs, outflows and other kinematic components to the FIR emission. Mapping an additional high-J CO line allows us to further distinguish high-excitation outflows from PDRs. Since the FUV radiation illuminating the PDRs is dominated by a single O7.5 star in the emission nebula, and is hence well characterized, we can then compare published models with the PDR contributions to the FIR lines.

Proposal ID: 09_0117

Principal Investigator: Zhi-Yun Li (University of Virginia)

Title: Mapping Dust Polarization of a Dense Cluster-Forming Filament in the Best Magnetically Characterized Giant Molecular Cloud Vela C with HAWC+

Abstract: With thousands of polarization vectors from BLASTPol, the Vela C molecular cloud is an ideal lab for exploring how magnetic fields affect the structuring of cloud material and the formation of stars. We seek to connect the cloud-scale magnetic fields revealed by BLASTPol to those on the smaller scales that are more directly involved in star formation by mapping dust polarization of the cluster-forming filament Vela C SR-1 with HAWC+ in Bands E and D. We will examine the correlation between Herschel column density map, APEX and Mopra molecular line observations (obtained in private communication), and HAWC+/BLASTPol inferred magnetic field morphology, in order to estimate the relative importance of magnetic fields, gravity, and turbulence on all scales ranging from dense cores (0.05 pc) to the whole cloud (40 pc). Complementary ALMA polarization data on the 0.01 pc scale are already in hand (obtained in private communication) for the densest protostellar cores in the filament. Multi-scale non-ideal MHD simulations, led by the PhD student on the project, will be used to aid the interpretation of the multi-scale polarization and molecular line observational data, as a central part of his/her PhD thesis.

Proposal ID: 09_0119

Principal Investigator: James Jackson (SOFIA)

Title: Investigating [O I] 63 micron Absorption Using [O I] 145 micron Emission

Abstract: Much recent evidence shows that toward cold, dense molecular clumps, the ground-state [O I] 63 micron line can in fact be optically thick and absorb background [O I] 63 micron line emission from a PDR. This absorption can reduce the measured [O I] 63 micron signal so much that the PDR parameters derived from models using the observed [O I] 63 micron fluxes become unphysical and meaningless. The [O I] 145 micron line, however, is not absorbed, and thus should provide the actual unattenuated [O I] line shapes from the PDR. The team will use GREAT to measure [O I] 145 micron line profiles at high angular (13") and spectral (1 km/s) resolution toward three star-forming regions known to have significant [O I] 63 micron absorption or self-absorption: DR21, W49N, and G337.95-0.47. This program will take advantage of the new ability of GREAT to measure [C II] and [O I] 145 micron simultaneously in the LFA, and [O I] 63 micron in the HFA. The [O I] 145 micron line profiles will be used as a template emission line shape to identify absorption features in the [O I] 63 micron line and to measure their optical depths. The [O I] 63 micron line fluxes can then be corrected to produce meaningful results in PDR models.

Proposal ID: 09_0121

Principal Investigator: Kate Su (University of Arizona)

Title: The Inner Warm Debris in the Vega Planetary System

Abstract: Debris disks -- discovered as "the Vega Phenomenon" -- provide the best means to explore planetary system evolution. The locations of the leftover planetesimal belts, similar to the asteroid and Kuiper belts in our solar system, can indicate where the giant planets formed and their migration history. As one of the first discovered debris disks, the Vega system is extensively studied, revealing complex debris structures. Existing SOFIA data at 35 micron detect extended warm excess emission that could arise from either in-situ, asteroidal-like planetesimal belt(s) or cometary dust from icy planetesimals scattering inward from the Kuiper-belt analog. We propose to obtain a 25 micron SOFIA image of this iconic system to assess the nature of the warm debris.

Proposal ID: 09_0122

Principal Investigator: Dario Fadda (USRA)

Title: Unveiling the dark side of collisional ring galaxies

Abstract: We propose to observe with FIFI-LS two extraordinary collisional ring galaxies: Cartwheel and AM0644-741. A particular kind of interacting galaxies, they originate by head-on collisions with a nearby galaxy close to their centers. Such slow collisions do not disrupt the morphology of the galaxy but create density waves expanding radially through the disk. As the waves propagate through the disk, they compress and shock the gas in their way triggering a massive formation of stars, such that these two galaxies are among the brightest galaxies observed in the UV with GALEX. Although abundant molecular gas is expected to accumulate in the rings, they appear dark (Cartwheel) or under-luminous (AM0644-741) in CO. The reason of this is not clear. We propose to observe the [CII] emission with the following objectives: (1) explore the [CII] emission in the ring comparing the star-formation rate from optical and IR observation to the estimate based on [CII], (2) study the mechanism behind the [CII] emission to see if the emission is dominated by star formation or enhanced by shocks in the gas, (3) unveil possible CO-dark molecular clouds in the ring and, possibly, in the filaments of gas flowing from the outer ring back to the nucleus. In addition to shed new light on the evolution of collisional ring galaxies, this study has also a more general significance because of the ubiquitous presence of interacting galaxies in the distant Universe. [CII] can be used as a reliable tracer of star formation especially if it traces also dark molecular gas. On the other hand, if shocks significantly boost the [CII] emission, it can be a biased tracer.

Proposal ID: 09_0129

Principal Investigator: Sarah Nickerson (NASA Ames Research Center/BAERI)

Title: The Molecular Heart of Hot Cores

Abstract: The mid-infrared (MIR) provides the only access to rovibrational transitions and molecules with no permanent dipole moment. Compared to longer wavelengths in the radio, sub-mm and far-infrared, the MIR uniquely probes hot core material closest to embedded protostars. Nonetheless, the MIR has historically been underutilized in analogous astrochemical studies for reasons including atmospheric interference and low available spectral resolution from previous space missions. Most high spectral resolution line surveys have been limited to radio, sub-mm and far-infrared wavelengths. Accordingly, the model chemical networks have never been published or tested for the MIR regime. We propose a SOFIA/EXES molecular line survey of three chemically and morphologically diverse hot cores: AFGL 2591 VLA 3, Mon R2 IRS 3, and W3 IRS 5 by targeting key bandpasses between 7.4 and 25.7 micron that have been found to be molecular-rich in the hot core Orion IRc2. Comparison of archival EXES spectra between these hot cores show differences in the chemical species and their abundances. This proposed work, combined with archival data at shorter MIR wavelengths (5.4 to 8 micron), will lead to the first high resolution MIR spectral line database for hot cores. These spectra will yield rich information on the hot cores' physical conditions, including structure, orientation, age, temperature, and molecular abundances. Comparisons between our three proposed targets and three from archival data, Orion IRc2, NGC 7538 IRS 1, and AFGL 2136, will provide unique insights into the interplay between a massive protostar's age and environment, and the molecular signatures in the hot core that envelops it. Such a comprehensive data set will serve as an invaluable, and first of its kind, reference for the astrochemical scientific communities. We will make our SOFIA data public immediately to allow astronomers to refine their chemical models and make more accurate predictions for future JWST observations.

Proposal ID: 09_0131

Principal Investigator: Jeroen Bouwman (MPIA Heidelberg)

Title: The nature of crystalline silicates in the protoplanetary disk of AB Aurigae

Abstract: We propose to observe the circumstellar disk in the Herbig Ae/Be system AB Aurigae with the FIFI-LS spectrograph. Specifically, we want to target the 69 micron region, where a spectral feature of the crystalline variety of the iron-magnesium silicate Olivine leaves its mark. The derived shape, width and exact wavelength centroid of this spectral feature can be exploited to infer the temperature during the grain formation as well as to constrain the ratio of iron to magnesium in these silicate grains. This in turn gives decisive insights into the thermal and chemical conditions when these grains formed. For our target, Herschel/PACS observations had indicated the existence of the 69 micron emission feature for that disk, but those observations achieved just a relatively low signal-to-noise ratio, and the ambiguous feature fit placed this object in a peculiar part of the parameter space. Such spectral dust features are much broader than common gas spectral lines, and hence a moderate spectral resolution is sufficient to do such a measurement. The FIFI-LS instrument is thus perfectly suited to attempt such an observation for which we will employ a spectral scan with a wide sweep of 3 micron to cover the feature. No other active facility is currently able to do such a measurement. It will settle the question whether AB Aurigae is indeed a special disk in terms of its dust properties. If the PACS indication for Iron enhancement in the dust of AB Aur is confirmed this would imply that beside the normal high-temperature gas-phase condensation, also alternative slower routes via parent-body type alterations can occur already in the protoplanetary stage. Our proposal can be a pathfinder to further such observations with FIFI-LS.

Proposal ID: 09_0134

Principal Investigator: Javier Goicoechea (CSIC)

Title: Velocity-resolved OH emission from Orion BN/KL outflow(s)

Abstract: The energy and momentum injected by radiation and outflows from massive protostars drastically affect their natal molecular cloud environment. These feedback processes locally regulate the formation of new stars and contribute to the cycle of matter and energy in galaxies. Far-infrared OH P-Cygni line profiles are a powerful probe of molecular outflows (either emerging from protostars, mergers, or galactic outflows) and a proxy of shocked H2 gas. Herschel observations showed that OH lines are a signature of a new class of shocks affected by UV radiation (different structure, chemistry, and enhanced OH/H2O relative abundances). However, owing to the modest spectral resolution of PACS, it was not possible to study the spatial and velocity structure of a prototypical outflow in OH. We propose to use GREAT to obtain fully-sampled velocity-resolved maps of the OH fundamental rotational line (at 119 μm) and of the high-J CO 13-12 line toward the bright explosive outflow(s) in Orion BN/KL. Since the late '70s, this field-of-view has been an excellent laboratory to study massive star-formation and the processing of cold molecular gas by shock waves. The same FoV has been mapped with HST, ALMA, SOFIA/HAWC+, and at high velocity resolution with Herschel/HIFI (in several H2O, mid-J CO, [CII], and CH+ lines) and IRAM 30m (in tens of lines of oxygen-rich complex molecules at different velocities) telescopes. This will be the first time that OH line profiles will be both spatially and spectrally resolved across such an iconic molecular outflow, and directly compared to a long list of existing velocity-resolved maps, dust thermal and dust polarized emission images. The requested GREAT maps will allow us to constrain the physical conditions and column densities in different velocity bins of the flow(s), and to determine the nature of the shocked gas by testing state-of-the-art "UV-irradiated" and "self-irradiated" shock models.

Proposal ID: 09_0135

Principal Investigator: Antonine Gusdorf (LPENS; École Normale Supérieure; Paris Observatory)

Title: The far-infrared view of the Cepheus E protostellar outflow

Abstract: Protostellar jets and outflows play a critical role in the evolution of the interstellar medium (ISM) of galaxies, in which they input energy in all possible forms: mechanical through the shock waves they drive, far-UV photons from the protostar or from the fastest shocks, and cosmic rays (CRs) that can be locally accelerated. Mapping the Cepheus E outflow from an intermediate-mass protostar in the far-infrared (FIR) range will allow us to better understand the physical processes associated to the outflow structures, as well as their energetic and chemical impacts. It will also allow us to probe the formation process of the young star and its outflow. Finally it will provide constraints to study the possible acceleration of particles in its energetic shocks. We request to map the entire outflow in the [OI] 3P1-3P2 and [CII] 2P3/2-2P1/2 lines. Combined with recent observations, they will be analysed in four steps. First, simple assumptions will be adopted (local thermodynamical equilibrium then large velocity gradient) to measure column densities and energetics. Then, the public Paris-Durham shock model will be applied to better understand shock physics and chemistry in local knots. At this stage, we will compare the outflows characteristics to models of outflows formation. Finally, a model of particle acceleration will be used to assess the potential of this outflow to generate cosmic rays A map of an entire protostellar outflow in [OI] 3P1-3P2 at 6'' resolution (and in [CII] 2P3/2-2P1/2) will be an unprecedented showcase of SOFIA's capabilities, and bear valuable scientific information. We will propose to map H2 lines with the JWST, as they provide excellent and complementary diagnostics in Cep E.

Proposal ID: 09_0136

Principal Investigator: Jochen Eislöffel (Thüringer Landessternwarte)

Title: Deciphering the periodically outbursting masers in G37.55+0.200

Abstract: Recently, accretion bursts of massive young stellar objects (MYSOs) have been identified to cause flares of Class II methanol masers due to mid-IR pumping. This opens a new window to gain knowledge on protostellar accretion variability. It implies that periodic methanol masers hint at cyclic accretion, possibly caused in a YSO binary source. We derived the first IR light curve of one of the rare periodic maser hosts from NEOWISE data and the contemporary maser lightcurve with the Torun 32-m radio telescope. The source, G107.298+5.639, is an intermediate-mass YSO hosting methanol, water, and hydroxyl masers which flare every ~34.5 days. With the Flash Call for FIFI-LS we could show in a feasibility study that the source spectral energy distribution (SED) is rising out to the far-IR, which allowed us for the first time to determine the accretion driven energy input for the maser flares. With this proposal we are requesting FIFI-LS observations for a second, more massive, methanol maser burster, G37.550+0.200. This high-mass YSO is currently the only object where maser periodicity has been found for three different, most likely IR-pumped maser species (CH3OH, excited OH, and H2CO). With two observations near to the maximum and near to the minimum of the burst cycle we will be able to derive the SED and its possible variability -- as well as a few crucial emission lines tracing warm dense gas -- of this prototypical source. With these data we will derive the accretion rate and the energy input available to pump the maser emission. This will allow us new insights in the emerging field of using methanol masers as signposts to the dynamics of the accretion-driven growth of massive stars and compare to latest high-mass binary formation models.

Proposal ID: 09_0137

Principal Investigator: Frédéric Schuller (AIP)

Title: Probing the structure and dynamical role of the magnetic field in the NGC 6334 massive filament region

Abstract: Recent observational results with, e.g., Herschel and Planck support a paradigm of star formation in which magnetized, thermally-supercritical filaments play a central role. The internal dynamics and magnetic properties of such filaments remain poorly constrained, however. We propose to use HAWC+ in Band E to map, for the first time, the plane-of-sky magnetic field at ∼18′′ or ∼0.15 pc resolution in two fields of view (FOVs) encompassing the bulk of the NGC 6334 main filament and its immediate vicinity. This filament stands out as it is very dense, with a line mass ~1000 Msun/pc exceeding the thermal critical line mass by almost two orders of magnitude, and appears to form unusually massive cores according to recent ALMA results. With HAWC+ polarization data, we aim to confirm our hypothesis that the remarkable properties of the NGC6334 filament are due to a strong, dynamically important magnetic field. More specifically, we will discriminate between two extreme models for the dynamical state of the filament: (1) a quasi-equilibrium model in which the magnetic field is strong and the field lines are only slightly distorted at the locations of dense clumps seen with APEX/ArTéMiS along the filament, and (2) a dynamical model in which the filament is essentially an accretion flow, and the field lines are dragged along the flow/filament.

Proposal ID: 09_0143

Principal Investigator: Maitraiyee Tiwari (University of Maryland College Park)

Title: Studying the effects of stellar feedback in RCW 49

Abstract: The interaction of massive stars with their environment is a key driver of the evolution of the interstellar medium of galaxies both in the local universe as well as at high redshifts. With this proposal we wish to observe OI 63 and 145 μm lines toward RCW 49, which is one of the brightest massive star-forming regions in the southern Galaxy. With the available archival data of diffuse X-ray (Chandra), radio, IR (WISE, GLIMPSE, Spitzer and Herschel), sub millimeter (APEX) emission toward RCW 49, we aim to perform a comprehensive multiwavelength study to quantify the feedback in the RCW 49 HII region powered by the rich Westerlund 2 cluster. This study can also act as a template for future studies to understand stellar feedback in the Interstellar medium of the Milky Way and other galaxies. The major cooling lines of a PDR are the fine-structure lines of CII and OI observable in the far-IR. With the user ready CII data available in the SOFIA archive, we need the OI lines to complete our study of the PDR of RCW 49. Both 63 and 145 micron lines are important, the former being brighter but optically thick while the latter is mostly optically thin and is important for the interpretation of opacity effects. Analysis of these high resolution (spatially and spectrally) observations together with a comparison to theoretical photodissociation region (PDR) models, will allow us to probe gas temperature and density, and the FUV flux incident on the gas.

Proposal ID: 09_0145

Principal Investigator: Greg Sloan (Space Telescope Science Institute)

Title: Pulsation and Dust in Galactic Carbon Stars

Abstract: Context - This proposal will investigate the relation between stellar pulsation and the production of dust and molecules in the outflows from Galactic carbon stars. These stars dominate the measurable contribution of dust in nearby Local Group galaxies and are a major contributor in the Milky Way. They are also an important source of fresh fusion products. Understanding how they die will improve our understanding of the dust ecosystems and chemical evolution of entire galaxies. Aims - We will obtain infrared spectra with the FORCAST grisms of a sample of 17 Galactic carbon stars pulsating as SRa variables to probe the relation between stellar pulsation and mass loss and dust production. Methods - We will compare the properties of the dust and molecules in our sample with carbon-rich Miras and SRb variables to test conclusions from previous observations that the strength of the pulsation mode determines the quantity and composition of the dust and its molecular building blocks. Synergies - The proposed infrared spectra will be analyzed in the context of similar data from the Infrared Space Observatory and Spitzer Space Telescope and set the stage for future work with the James Webb Space Telescope. Anticipated Results - The proposed spectra will provide a direct test of the role of pulsation amplitude on the formation of molecules and the production of dust in Galactic carbon stars.

Proposal ID: 09_0146

Principal Investigator: David Chuss (Villanova University)

Title: Deciphering the Radiative and Magnetic Environment of the Sagittarius B2 Molecular Cloud

Abstract: We propose to map the Sagittarius B2 (Sgr B2) molecular cloud using all four bands of the HAWC+/SOFIA instrument. Sgr B2 is the only reported case for polarization by absorption in the FIR, which has been modeled assuming warm embedded sources are selectivly absorbed by a cool foreground layer containing magnetically-aligned dust grains. The proposed observations will provide a rich polarimetry data set at unprecedented level of sensitivity and resolution. These data set will allow a detailed study of the radiative environment of this important star forming region in the Galactic center. We will use MCMC techniques to model the cloud over various sightlines to constrain the physical properties of the warm star-forming cores and the cool foreground dust layer. We will also utilize the DCF technique to extract information about the strength of the magnetic field to determine the implications for the magnetic effects on the star formation process.

Proposal ID: 09_0148

Principal Investigator: Guido Fuchs (University of Kassel)

Title: High resolution IR observations towards VY Canis Majoris – Investigations on SiS HCN and NH3

Abstract: VY Canis Majoris is an extreme oxygen-rich red supergiant with a large infrared excess, making it one of the brightest objects at infrared wavelengths. The star is rapidly losing mass via strong stellar winds and is surrounded by a dusty shell with a rich molecular content close to the star with around 25 molecular species found to date. There are several distinct dynamical regions with different molecular content. So far, most molecule detections have been performed at radio and submm wavelengths. Only a few molecules, like CO, SiO, H2O and NH3 have been seen in the IR region towards this source. Here we propose to try to detect for the first-time in the infrared SiS and HCN. The detection of these molecules would give new insights into the dynamics of the circumstellar matter and is an important test for chemical models of oxygen rich late-type stars. In addition, we would like to observe NH3 as it is a key molecule that connects spectral regions in the mid-IR that are far apart, like those from SiS (780cm-1) and SiO (1150cm-1). Furthermore, NH3 is also seen at MW or THz frequency ranges. It is thus an important diagnostic and will be used to intensity calibrate the IR spectra and make comparisons to other frequency regions. We aim to systematically perform high-resolution resolution (R> 60,000) IR observations using the EXES spectrometer to investigate the molecular content of VY CMa in the vibrationally excited state and to gain insight in the dynamics and chemistry of the envelope of this late-type star. The high spectral resolution of EXES is needed to resolve the ro-vibrational spectra of the targeted species. Ground based observations in this frequency range are strongly hindered due to the terrestrial atmosphere but will be feasible with SOFIA. This project supports a previous cycle 8 proposal (08_0176) and is also part of an infrared line survey of VY CMa.

Proposal ID: 09_0149

Principal Investigator: Serina Latzko (University of Stuttgart)

Title: Revealing the mysteries of CII in the outflows of M82

Abstract: Starburst driven outflows and winds are features that have been observed in connection with starburst events. The processes and mechanisms, however remain unclear due to the very high extinction of the centres of those galaxies. For a long time the [CII]158 µm emission line was thought to be a good tracer for star formation only. However, in many galaxies observations reveal that [CII]158 µm emission arises from almost everywhere in the galaxy. M82 with its proximity and its intense starburst is one of the best candidates to find an answer to the question which mechanisms are responsible for the occurrence of the [CII]158 µm emission we see all over the galaxy. With this proposal we are in particular addressing the origin and characterisation of the [CII]158 µm emission in the outflow and the disk of M82.

Proposal ID: 09_0150

Principal Investigator: Jorge Pineda (JPL)

Title: What is the Source of the Ubiquitous Dense Ionized Gas Throughout the ISM and Does it Impact [CII] as an SFR Tracer?

Abstract: Context: Herschel and SOFIA [NII] observations have revealed the presence of a ubiquitous dense ionized gas component in the Galactic plane. This medium can be the dominant source of [CII] and [NII] emission in galaxies, and thus its characterization is important for the interpretation of observations of these lines in distant galaxies and for characterizing the UV energy sources in galaxies. Aims: We propose to use FIFI-LS on SOFIA to observe the [NIII] 57µm line along 8 lines-of-sight that have been observed in [NII] 205µm and 122µm, [CII], and hydrogen radio recombination lines. These data will be used to constrain the EUV radiation field and determine the total nitrogen abundance as a function of Galactocentric distance. Synergies: The [NIII] 57µm observations will be combined with a multi-wavelength set of observations including Herschel, SOFIA, NASA's Deep Space Network 70m antenna, and the Green Bank Observatory. The proposed work will also provide important constraints to theoretical models on the ionization sources in the Galaxy and the formation and evolution of the Milky Way. Anticipated Results: We will combine the [NIII] 57µm observations with those of [NII] 205µm and 122µm to measure the abundance of the two ionization states. We will then be able to determine the strength of the extreme ultraviolet (EUV) radiation field required to explain this ratio of ionization states. This quantity will distinguish among different models proposed to explain the dense ionized gas and evaluate the role of EUV in galactic evolution. Additionally, we will use this data set, and that of [NII] 205µm and 122µm and hydrogen recombination lines, to determine the total nitrogen abundance relative to hydrogen as a function of Galactocentric distance. This abundance ratio is an important quantity for understanding the star formation history of the Milky Way, and to constrain models of its formation.

Proposal ID: 09_0151

Principal Investigator: Michael Gregg (U.C. Davis)

Title: Detecting the Interstellar Medium of Globular Clusters

Abstract: Milky Way globular clusters are swept clean of any intracluster gas and dust by passing through the Galactic disk ISM. During the 100 million year interval between such disk passages, a typical cluster will accumulate about 100 solar masses of gas from mass loss from evolved red and asymptotic giants, most of which should be retained by the gravity of the cluster. This material has yet to be detected and the fate of the stellar mass loss remains a mystery. This proposal requests time with FIFI-LS to observe a sample of three Milky Way globular clusters predicted by new models to have appreciable gas. The primary aim is to detect and measure the strength of [CII] 158 micron emission to derive the properties of the interstellar material. Because [CII] is 10-100 times more sensitive than other methods, these far-IR observations have a better chance of detecting the ISM in globulars, and will at least establish new upper limits. With robust detections, other emission lines may be measurable, aiding in the determination of the temperature, density, and state of the globular cluster ISM.

Proposal ID: 09_0152

Principal Investigator: Jorge Pineda (JPL)

Title: The Impact of Extreme Stellar Feedback on the Dynamics of Neutral Gas Clouds in the Carina Massive Star Forming Region

Abstract: Stellar feedback plays a fundamental role in the regulation of star formation in galaxies by injecting energy into the star forming interstellar medium (ISM) gas, and is, thus, an important driver of their evolution. The main unknown in the role of feedback on regulating star formation is the efficiency with which the available energy and momentum couples to the surrounding gas. To determine the coupling of stellar feedback to their surrounding ISM, we need large scale, high dynamic range, high spectral resolution observations of key tracers of the neutral ISM with [C ii] 158um and [O i] 63um in star forming regions. The [C ii]158um traces a wide range of conditions in the neutral ISM, while [O i] selects out warm, dense photon dominated regions (PDRs). We propose large scale, high dynamic range, high spectral resolution [Cii] 158um and [Oi]63um maps with upGREAT in the entire Carina nebula to measure the influence of feedback from massive star formation in the neutral interstellar medium (ISM). upGREAT on SOFIA is currently the only instrument that can provide this scale of mapping. The Carina nebula is one of the most active star forming regions in the Milky Way, and therefore represents an ideal nearby laboratory to study radiative and mechanical feedback, and the properties of the ISM, in extreme star formation environments. Carina represents a template for the interpretation of observations of similar regions in external galaxies ,such as 30 Doradus in the LMC, that can be studied at high spatial resolution. The Carina region will be also mapped by the ASTHROS balloon at comparable angular and spectral resolution, over the same large scales, in ionized gas tracers, [N ii] 205um and 122um, which will be used to characterize the properties and dynamics of ionized gas in these regions. The combination of the SOFIA, balloon borne, ancillary Herschel, Spitzer, and ground based data sets, will make possible to obtain a complete picture of the dynamics and distribution of ionized and neutral gas, and their interrelation, as influenced by stellar feedback. The [C ii] and [O i] data set in the Carina nebula will be used to search for gas outflows, to quantify the kinetic energy injected by stellar feedback into the ISM, and to search for CO-dark H2 to study the earlier stages of molecular cloud formation. This data set will be also analyzed using statistical tools and will be compared with numerical simulations of interstellar gas under the influence of stellar feedback. We therefore expect that this program will deliver important insights on the cycle of matter and star formation in the Carina nebula.

Proposal ID: 09_0155

Principal Investigator: Samantha Scibelli (University of Arizona)

Title: Far-IR Dust and Magnetic Field Alignment Study of the Collapse Candidate Starless Core L63

Abstract: Modeling the internal structure and dynamics of prestellar cores is crucial for understanding their evolution up to the initial stages of disk and protostar formation. An evolved core, especially one on the brink of collapse, will reflect the primordial conditions of star formation without contamination from protostar outflows. L63 is a unique prestellar core in that it has prominent infall or collapse signatures, yet it was not targeted by Herschel due to its remote location in the Ophiuchus molecular cloud. We propose to utilize the SOFIA HAWC+ instrument to take polarimetry and total intensity measurements of L63. We will 1) measure relative magnetic field alignment to compare to modeled infall structure and 2) constrain from total intensity measurements at 154micron and 214micron the peak of L63's SED. We also ask for time, as part of the joint proposal process, to obtain high resolution (11'') HCN 1-0 observations with ARGUS on the GBT to study this cores' infall profile at high spatial resolution. These observations will be an integral piece of thesis work, which will include multi-dimensional continuum and line radiative transfer modeling on prestellar core L63, exploring both physical and chemical conditions.

Proposal ID: 09_0158

Principal Investigator: Laura Lenkic (University of Maryland Baltimore County)

Title: Local Analogues of Turbulent Clumpy Main-Sequence Galaxies at the Peak of Cosmic Star Formation

Abstract: This proposal aims to characterize the properties of the neutral gas and HII regions in a sample of nearby, clumpy, turbulent galaxies. The properties of these galaxies most closely resemble those of z ~ 1 – 3 galaxies, when star formation activity was at its peak. The galaxies selected for this proposal are from the DYNAMO sample of galaxies from Green et al. (2010). Their disks have high internal velocity dispersions and high gas mass fractions much like z ~ 1 – 3 galaxies, and have star formation rates ranging from 10 to 80 solar masses per year. This gives us a unique opportunity to study the neutral interstellar medium in this turbulent, clumpy environment, without the difficulties that are encountered in high redshift studies. We will use FIFI-LS to observe the 157.7 µm [CII] and 88 µm [OIII]/63 µm [OI] fine-structure lines, and use HAWC+ observations in band C, D, and E to derive the total far-infrared luminosities and estimate the FIR dust temperatures. We will use the combination of [CII] and FIR observations to do photodissociation region modeling and derive the gas densities and far-ultraviolet radiation field strengths, and [OIII] to study the properties of HII regions. We will also derive star formation rates from the total FIR luminosity and use these to test [CII], [OIII], and [OI] as star formation rate tracers. These lines are observable by instruments such as ALMA at higher redshift and are potentially powerful probes of the ISM and tracers or star formation. This proposal will fill a void in the existing multi-wavelength studies of DYNAMO galaxies which include observations from ALMA, NOEMA, Keck, Gemini, and HST.

Proposal ID: 09_0159

Principal Investigator: Niko Zielinski (Institut für Theoretische Physik und Astrophysik; Christian-Albr)

Title: Constraining radiative torque alignment efficiency using SOFIA/HAWC+

Abstract: Context - The impact magnetic fields may have at various stages of star formation is a matter of open debate (e.g., Seifried & Walch 2015). Polarimetric observations are one way of addressing this issue, as it is generally accepted that non-spherical dust grains align with the magnetic field. Given an anisotropic radiation field (e.g., by the presence of a star) radiative torques (RATs) are discussed to play an essential role in the alignment process. In order to be able to make reliable statements about the underlying magnetic field structure and strength, the RAT mechanism must be understood in detail (e.g., Hoang & Lazarian 2008). Aims - We aim at constraining the efficiency of RAT alignment. For this purpose, we propose to perform observations of the dense core L43 with SOFIA/HAWC+ (bands D/E) to extract a polarization spectrum (e.g., Hildebrand et al. 1999; Michail et al. 2020). Methods - Based on the SOFIA/HAWC+ observations and existing 850 μm SCUBA observations (Matthews et al. 2009) we will derive the wavelength-dependent spatially resolved thermal re-emission polarization pattern. Applying polarization radiative transfer simulations, including self-consistent treatment of the dust heating and re-emission, as well as alignment due to RATs and the stellar and interstellar radiation fields, we will derive the best-fit-model for the density, dust phase and local radiation field. Based on this model, we will constrain the efficiency of the alignment process by RATs. Anticipated results - We will derive constraints for the efficiency of the RAT mechanism. These observations are of fundamental importance for the interpretation of polarization data in general if magnetically aligned dust grains are assumed, regardless whether the polarimetric data was obtained on a large scale with SOFIA/HAWC+ or on small scales with ALMA.

Proposal ID: 09_0160

Principal Investigator: Aaron Bryant (DSI)

Title: Probing the Evolutionary Chain of Molecular Clouds in the Central Molecular Zone

Abstract: The central molecular zone (CMZ) of the Milky Way extends from around -1.5° to +1.5° in longitude, and is host to a 100 pc scale stream of molecular clouds and star clusters, which has been postulated to represent an evolutionary chain of ISM chemistry and star formation. We propose to further analyse the nature of the stream by characterising the physical conditions of the dense ISM in the various molecular clouds and star-forming sites. We will observe the far infrared spectral lines that are typical diagnostics of the dense ISM and tracers of star formation or mechanical heating close to the gas, including [CII], [OI], [OIII], [NII], and CO. Together, these lines span a range of physical states of the dense gas, and can serve to show the evolutionary states of the structures they are observed in. We will utilise the fast mapping capability and high angular resolution of the integral field spectrometer FIFI-LS to obtain maps of these lines for all targets in a flexible and efficient manner, without the need to change instrumental configuration between flights. We expect to obtain a series of spatially resolved line flux maps in each of the spectral lines of interest, for as many of the 100 pc stream objects as can be observed. The relative strengths and distribution of these fluxes will reveal information about the physical nature of the dense gas and radiation field. This will assist us in our characterisation of the relative state of each of the objects, and the extent to which they are truly related on this evolutionary chain.

Proposal ID: 09_0161

Principal Investigator: Laure Bouscasse (Max Planck Institute for Radio Astronomy; Bonn)

Title: Water deuteration in the outer envelope of hot core precursors

Abstract: High-mass star formation is still an enigma in modern astrophysics. SPARKS is a follow-up with ALMA targeting the most massive and youngest clumps in ATLASGAL. The high angular resolution observations reveal several sources which are isolated from 0.3pc down to 2000au: one of them is AGAL328.2551-0.5325. This makes them relatively easy targets for single-dish observations to study the early warm-up phase chemistry leading to the appearance of classical hot cores. Using APEX, we performed an unbiased spectral survey towards these objects, and revealed the molecular composition of their envelopes (e.g. cold, warm layers, shocks) depicting a significant molecular diversity. Among the deuterated molecules, HDO is the only molecule detected in the warm envelope at temperature of ~100K. Its deuteration ratio is found to be high (~0.8%) compare to low-mass protostars. Here we target key lines of HDO (509GHz and 1009GHz lines) and H218O (547GHz and 994GHz lines) in order to allow meaningful excitation studies of these important molecules in the outer envelope with 4GREAT/SOFIA. We will use these lines to constrain the deuteration ratio in the outer envelope and compare to the already obtained data targeting the inner envelope with APEX. A complete study of the deuteration in the outer envelope is key to constrains the water formation pathways in the gas phase.

Proposal ID: 09_0162

Principal Investigator: Marta De Simone (University of Grenoble)

Title: Water content in the early stages of planet-forming regions

Abstract: The presence of water on an extraterrestrial planet is a crucial condition for its habitability. This small molecule also plays an important role in the star formation process allowing clouds to collapse into stars acting as a major gas coolant and helping the coagulation of icy dust grains in planetesimals and, eventually, planets. Although very abundant in star forming regions, water is mostly frozen, except in warm enough zones, where water ices sublimate and becomes observable via its rotational lines. In Solar-type protostars, the water-ice-sublimated regions are called hot corinos. The abundance of water there, and more specifically in the Class I protostars where planets start to form, is unfortunately poorly known. SOFIA/EXES is currently the only available facility that provides sufficient spatial and spectral resolution to detect water line emission originated in hot corinos and to measure its abundance. Following ad hope model predictions, we propose to observe several rotational water lines at 22.5-26.5 micron toward the only Class I hot corino where evidence of water presence is so far known, NGC 1333 SVS13-A. The requested observations will allow us to perform a multi-line analysis, using sophisticated radiative transfer models, in order to derive the SVS13-A hot corino properties, and the water abundance. In other words, it will be possible to measure how much water is available in regions where planets start to form.

Proposal ID: 09_0163

Principal Investigator: Noel Richardson (Embry-Riddle Aeronautical University)

Title: The spectroscopic signature of new dust forming around WR137

Abstract: Classical carbon-rich Wolf-Rayet (WCd) stars are often found in binary systems where the winds of the WCd star and an O star companion can collide, mix, and form dust. Dust formation in WC binaries occurs on short (millions of years) timescales and can occur even in environments near zero metallicity, so it's feasible that WCd binaries may have played an important role in producing the first dust in the Universe if the star formation processes were similar and produced large numbers of massive binaries. Thus, our understanding of these rare systems may be of cosmological importance. We propose a program to observe the long-period, dust-forming, Wolf-Rayet binary WR137 as it approaches its next periastron passage. The stars in this system are well studied and have even been interferometrically resolved, allowing us to pinpoint many physical and chemical processes that contribute to dust formation. Our proposed SOFIA observations during Cycle 9 will enable a search for the spectroscopic signatures of the precursor molecules created early on in the dust formation episode. We will fit the SED from the dust in order to understand the molecular composition and temperature as the wind collision density increases as the stars approach periastron passage and dust begins to condense. Very few WCd systems have been observed this early in a dust condensation episode, and these observations will be able to be compared with JWST/ERS observations made with NIRISS, allowing for both an understanding of the dust composition from SOFIA as well as its geometric distribution from JWST.

Proposal ID: 09_0164

Principal Investigator: Chi Yan Law (Chalmers University of Technology)

Title: Giant growing under still water: Polarized emissions from isolated massive protostar G28.20-0.05

Abstract: Massive stars are believed to play a crucial role in galaxy evolution, chemical enrichment of the interstellar medium, and the formation of black holes. Gravity, supersonic turbulence, magnetic fields, and feedback processes are main stakeholders in the formation of massive stars. Recent studies have shown that magnetic fields can play a dynamically important role in massive star formation. Magnetic fields may regulate the fragmentation of the parental cloud and the orientation of disks and outflows. The proposed observation aims to map the polarized dust continuum emission of an extremely isolated massive protostar G28.2-0.05 at four different wavelengths (53, 89, 154 & 214 um) with HAWC+. The derived polarization vector orientations will be studied, along with complementary molecular line data from the GBT, to infer magnetic field properties and their relation to gas density structures from the large scale IRDC filament to protostellar core and outflow scales. One way to explain isolated massive star formation is via the presence of very strong magnetic fields, i.e., to limit fragmentation, and this observation will test such a prediction.

Proposal ID: 09_0169

Principal Investigator: Yao-Lun Yang (University of Virginia)

Title: Probing the radiative cooling from shocks and PDRs in intermediate- and high-mass protostars

Abstract: The feedback from star formation affects the outcome of star formation. Particularly, formation of massive stars drives feedback into surrounding environment, regulating the ongoing star formation and the formation nearby. The UV radiation and outflows driven by massive star formation produce photodissociation regions (PDRs) and shocks around the forming massive protostars, resulting in rich spectra of atomic and molecular emission at far-infrared wavelengths. In particular, the emission of CO and [OI] dominates the far-infrared line luminosity of massive protostars, making them a unique tracer of the feedback from the outflow-core interaction. By measuring the far-IR transitions, we will constrain the properties of shocks and PDRs produced by the outflows of massive protostars and test the turbulent core model of massive star formation. Thus, we propose a survey program to utilize the FIFI-LS to observe [OI] 63 and 145 um lines, [OIII] 52 um, and CO J=14-13 lines to measure the energy budgets carried by CO and O, which are the dominate coolants in shocks and PDRs. From the sources already observed by the SOFIA Massive (SOMA) Star Formation survey, we will survey massive protostars in different environments to characterize the dominant cooling species. We will characterize the evolution of outflow-core interaction via the energetics measured from the far-IR emission. The measured far-IR cooling budget will test the protostellar properties estimated by the SOFIA Massive Protostars (SOMA) survey. Furthermore, we will collect archival observations of HST and ALMA to constrain the emission of jets via the emission of [FeII] and unveil the driving sources of jets. This program will measure the line fluxes of key cooling lines at far-IR wavelengths, probing the cooling budget in both PDRs and shocks for massive protostars in different environments.

Proposal ID: 09_0170

Principal Investigator: Jorge Pineda (JPL)

Title: Testing Theories of Spiral Arm Formation and Evolution in Galaxies

Abstract: The cycling of the interstellar medium among different phases, including the eventual formation of stars in gravitationally bound regions, is the driving agent in the evolution of galaxies. In spiral galaxies, spiral density waves play a fundamental role assembling the giant molecular clouds in which star formation takes place. However, exactly how the spiral density waves trigger star formation is unclear, with differing theories still not resolved. Velocity resolved mapping of [CII] in M51 has demonstrated the potential to answer these questions in spiral galaxies, but there is a need to extend such studies to a larger variety of galactic environments, in particular to those not influenced by tidal interactions. We propose to obtain a velocity-resolved [CII] image of the M94 isolated spiral galaxy with the upGREAT instrument on SOFIA. Previous work on mapping the entire M51 galaxy in [CII] has demonstrated that position/velocity information using [CII] and other tracers is a powerful tool to test theories of spiral structure in galaxies. But unlike M51, M94 has not been influenced by tidal interaction, and therefore makes it an ideal location for testing different theories of the nature of spiral arms in galaxies.The proposed observations will be combined with a multi-wavelength set of observations from several facilities including Herschel, Spitzer, and GALEX, and will certainly motivate follow up observations with current and future observatories such as NOEMA and JWST. The proposed observations are highly synergistic with SOFIA/HAWC+ observations of the magnetic field in spiral galaxies, as they both can trace dynamical effect produced by spiral density waves. Additionally, the proposed work will provide important constraints to theoretical models of star formation resulting from the passing of a spiral density waves in galaxy disks and on the structure of the interstellar medium in low-metallicity environments. The M94 data will be used to distinguish between competing theories of the nature of spiral arms. The combined M51 and M94 [CII] spectral images will constitute a legacy data set that will provide the community with detailed large scale [CII] spectral images of galaxies exposed to different environmental conditions and will allow comparison of star formation mechanisms in different environments.

Proposal ID: 09_0171

Principal Investigator: Paul Lucey (University of Hawaii at Manoa)

Title: Mapping the 6 µm Molecular Water Line Across the Lunar Surface

Abstract: SOFIA+FORCAST made an unprecedented detection of molecular water (H 2 O) on the lunar surface that raised new questions surrounding the behavior, formation, and storage of water on the Moon. Prior to this detection, it was suggested that water existed on the sunlit Moon and may be responsible for the variations observed in the 3 µm hydration band and UV water ice band ratio. However, it is unknown if the variations are caused by water or its close cousin hydroxyl (OH), which can spectrally mimic H 2 O at 3 µm. Spectroscopy at 3 µm and in the UV currently do not distinguish between water and hydroxyl. New methods were needed to uniquely detect H 2 O on the Moon. H 2 O features a fundamental bending mode at 6 µm that is strictly due to H 2 O without confusion from OH. However, the 6 µm spectral region is inaccessible from the ground, and measurements at 6 µm are lacking in existing or planned lunar spacecraft. The unique capabilities provided by SOFIA+FORCAST enabled the first detection of H 2 O on the sunlit Moon. At SOFIA's operational altitude, the low telluric atmospheric water vapor allows for observations of the Moon at 6 µm. Data obtained during a test flight in 2018 showed a strong 6 µm emission feature at high southern latitudes. This Legacy project will address fundamental questions raised by the detection of H 2 O on the sunlit Moon and produce maps of water across the Moon at multiple lunar times of day and of geologically important locations that may indicate the presence of interior water. The maps will inform us about the migration and storage of water and may be used to determine locations with high potential for resource extraction during the NASA Artemis and VIPER programs. The characterization of water on the Moon will be applicable to the understanding of water on other airless bodies in the Solar System and exoplanets.

Proposal ID: 09_0172

Principal Investigator: Maria S. Kirsanova (Institute of Astronomy; Russian Academy of Sciences)

Title: Tracing the PDR expansion and gas density distribution using the [OI] 63 and 145 micron lines

Abstract: Photodissociation regions (PDRs) around massive O and B-stars have several layers where C+/C/CO dominate in the total carbon budget. Theory predicts, the layers can be distinguished using spatially and spectrally resolved observations of PDRs. Simulations show that the PDRs expand together with their HII regions. Expansion of tenuous shells, where CO molecules can not survive, has been recently observed with the [CII] 158 micron line emission. However, these lines are optically thick in dense embedded PDRs, therefore, the new expansion tracers are needed to be found for that objects. We propose to study gas kinematics and density distribution using [OI] 63 and 145 micron transitions with SOFIA upGREAT in two PDRs where the layered structure and a signature of the expansion has been already found. We propose to complement the [OI] lines by CO(16--15) to study density gradient in the irradiated gas. We will compare position-velocity (pv) diagrams of the [OI] lines with available pv diagram based on SOFIA [CII] and [13CII] 158 micron lines and explore the kinematics of the PDR's layers. Spatial distribution of atomic oxygen column density will allow us to study density distribution on the PDRs because the [OI] line emission is a tracer of high-density gas. Comparison of the observed [OI] pv diagrams with theoretical results allows us to conclude if the [OI] 63 micron line is the reliable kinematics tracer in the dense PDR, as the theory suggests.

Proposal ID: 09_0176

Principal Investigator: Margaret McAdam (NASA Ames Research Center)

Title: Searching for molecular water on (24) Themis (2) Pallas and nominally anhydrous asteroids: contextualizing 3-µm detections of hydration on asteroids

Abstract: Hydration has been observed on asteroids in the form of water-ice frosts and hydrated minerals on low albedo asteroids. Recently, even nominally anhydrous objects may have 3-micron features indicating some hydration. The 3-micron spectral region, however, has a key degeneracy between molecular water and hydroxyls bound in hydrated minerals. Without complimentary observations, it is unclear whether asteroids with hydrated minerals have water-ice on their surfaces or if nominally anhydrous asteroids have exogenic molecular water or hydroxyls (either exogenic or from interactions with the solar wind) on their surfaces. Even for asteroid (24) Themis, which as been observed to have a water-ice frost, the abundance of water cannot be quantified with 3-micron observations alone. We propose to observe (24) Themis, (2) Pallas (a hydrated asteroids) and six nominally anhydrous asteroids with 3-micron bands searching for and quantifying the abundance molecular water, if detected, using SOFIA+FORCAST in the 4.9-8.0-micron region. Moreover, a detection or non-detection of water will be contextualized with mineralogy and thermophysical properties using FORCAST spectroscopy in the 8.4-13.7-micron and 17.7-27.7-micron spectral regions. Using these observations, the mineralogy of Themis and Pallas will be determined as well as the presence of molecular water, potentially constraining the different evolutionary histories of these asteroids. For the proposed S-type asteroids, the origin of the 3-micron features on these nominally anhydrous asteroids will be constrained. Since water and hydroxyl can contribute to the 3-micron band a detection of water may indicate exogenic water on the surfaces of asteroids rather than exogenic hydrated minerals or interactions between grains and the solar wind. The 3-micron band depth will be compared to the detection of molecular water to determine if water could be the only material causing these features on nominally anhydrous asteroids.

Proposal ID: 09_0180

Principal Investigator: Caitlin Casey (University of Texas at Austin)

Title: Precision Cosmology with SOFIA: Characterizing the Dust Emission in Nearby Supernovae Type Ia Host Galaxies

Abstract: We propose to directly measure the dust in SN Ia host galaxies to better understand how host galaxy ISM physics may impact precision supernovae cosmology. The physics of the ISM in and around Type Ia supernovae (SNe) is soon to become the dominant source of uncertainty as cosmological surveys enter an era of large statistical samples, with the Dark Energy Survey and VRO/LSST. Historically, SN cosmology has predominantly assumed a uniform reddening law to correct for dust extinction along the line of sight, both for dust in the Milky Way and in the host galaxy of the SNe. It has become apparent that there is a trend between host galaxy stellar mass and Hubble residuals (the residuals on the distance modulus) of unknown origin, and that dust in the host galaxies is suspected to be the root cause of this correlation. It is likely that an even stronger correlation between SN color and host galaxy dust mass, or Hubble residuals and dust mass, exists. Furthermore, there is tension between the measurement of the Hubble constant from local Cepheid calibrators (of which there are a total of 19 galaxies with both Cepheid and SNe Ia distance indicators), and Type Ia hosts embedded in the Hubble flow, which could be caused by host galaxy dust characteristics. We select a diverse range of 24 galaxies within D<100Mpc for resolved spatial observations of dust emission with SOFIA HAWC+ to directly infer correlation between line-of-sight dust mass towards the galaxies' SNe with residual measurements on their distances to inform future large SNe campaigns (more than tripling existing measurements). Six of the 24 targets are also Cepheid calibrators, enabling a more detailed study of line-of-sight attenuation toward both Cepheid and SNe Ia distance indicators. This is a resubmission of a successful cycle 7/8 program where partial observations were obtained. We are seeking completion of the program in Cycle 9, targeting 9 galaxies for a total of 8.4 hours.

Proposal ID: 09_0181

Principal Investigator: Nicholas Ballering (University of Virginia)

Title: Probing Protoplanetary Disk Dispersal with the 63 micron Oxygen Line

Abstract: The unique disk around HD 141569 is the midst of transitioning from a primordial protoplanetary disk to a debris disk. The 63 micron [OI] emission line was detected from this system with Herschel/PACS, but it was not spectrally resolved, so we have no constraints on where it originates. We will locate the source of this line by resolving its spectral profile with SOFIA/GREAT. In doing so we can ascertain whether the line originates from a photoevaporative wind or from the gaseous disk. The detection of a wind would provide evidence that photoevaporation likely plays a role in the final stages of disk dispersal. The 63 micron line is sensitive to cooler gas than typical wind tracers at optical wavelengths, so the line profile will provide new kinematic constraints on the wind-driving mechanism. If the line originates from the disk, its Keplerian profile will reveal the location of the emitting gas. Comparing this with the known location of molecular CO will reveal where the gas disk is photodissociating, while comparisons with the known features in the dust disk can highlight the role that radiation pressure plays in shaping this disk. Finally, our results will help to refine physical models of the disk to better understand the role that [OI], a powerful interstellar coolant, plays in setting the disk temperature.

Proposal ID: 09_0182

Principal Investigator: Nicholas Ballering (University of Virginia)

Title: Lurking Giants: Verifying and Characterizing Nearby Bright Debris Disks

Abstract: We propose a survey program to obtain HAWC+ photometry of 20 IRAS- and AKARI-detected bright nearby debris disks. IRAS and AKARI observations were prone to contamination from background sources, and none of these disks were observed in the far-IR with Spitzer or Herschel, so HAWC+ observations are critical to verify these sources as true debris disks. These bright nearby disks, once verified, are promising targets for future high-resolution imaging in the (sub-)mm with ALMA and in scattered light with HST, ground-based high-contrast instruments, and JWST. Nearby bright debris disks can reveal a wealth of information about the architectures, dynamics, and compositions of planetary systems. This SOFIA/HAWC+ program is a crucial stepping stone towards finding the next generation of targets for cutting-edge debris disk science.

Proposal ID: 09_0183

Principal Investigator: L. Ilsedore Cleeves (University of Virginia)

Title: Solving the Mystery of Missing Cold Water in Protoplanetary Disks

Abstract: Cold water vapor liberated from icy dust grains by UV photodesorption provides a unique view into the composition of protoplanetary disks' largely invisible ice reservoir. Surface H 2 O emission has been previously detected from this mechanism, though at a relatively weak level, far below predictions from models. However, interpretation of the weak emission into a water column density is limited by uncertain excitation modeling. To mitigate this, we propose to use the inclined disk RY Tau as a laboratory to study the primary photo-fragment of dissociated water, OH, in absorption. Based upon Herschel PACS observations of o-H 2 O toward RY Tau, the data are strongly suggestive of deep, spectrally unresolved self-absorption. We propose to confirm the nature of RY Tau's water and localize its radial distribution using spectrally resolved observations of 18OH with SOFIA GREAT. Specifically, UV photodesorption of water ice results in similar amounts of gas-phase OH as it does water, and thus by spectrally resolving the rarer and less optically thick 18OH's ground-state absorption line near 2.498 THz, we can finally constrain the distribution of ice-coated grains in this young disk system, and shed light on the question of whether the 'missing' water in disks is truly missing or just 'misplaced' spatially.

Proposal ID: 09_0185

Principal Investigator: Gordon Stacey (Cornell University)

Title: FIFI-LS Spectroscopy of Nearby IR Bright Galaxies: Tracing Stellar Populations; the N/O Abundance Ratio; and Absolute Abundances

Abstract: We propose to use FIFI-LS to map the [OIII] 52 um line emission from the central regions of 8 IR-bright nearby star forming galaxies including both normal and low metallicity systems. All but one of our sources has prior Herschel/PACS detections of [OIII] 88 um, [NII] 122 um, and [NIII] 57 um emission lines, Spitzer IRS detections or limits to the [NeII] 12.8 um, [NeIII] 15.5 um and [NeV] 14.3 um lines and radio free-free or hydrogen recombination lines. The sole incomplete source is NGC 2146, which is missing the [NIII] line, and we seek time here to observe this line with FIFI-LS. These observations will allow us to constrain the ionized gas density and mass, the hardness of the stellar radiation fields (hence most massive star on the main sequence), the N/O ratio (which reflects the numbers of cycles for star formation) and the absolute ionized gas phase N/H and O/H ratios which reflect the star formation efficiency integrated over time. We will also use Herschel archival [OI] 63 and 146 um, and [CII] 158 um data to characterize the neutral ISM and the strength of the FUV (6-13.6 eV) stellar radiation fields. In this way, we will have a continuous measure of the stellar UV radiation fields from 6 to 54 eV thereby constraining the numbers of upper main sequence stars. The proposed FIFI-LS [OIII] 52 um line observations are the lynch-pin that holds the analysis together. These measurements provide a local benchmark for our line-ratio techniques that can be applied to similar studies of high-z galaxies where it is expected that stellar radiation fields will be harder, and the N/O radio will be smaller for the lowest metallicity galaxies. Therefore, the proposed observations are fundamentally important to our understanding of the star formation process over cosmic time.

Proposal ID: 09_0189

Principal Investigator: Thomas Giesen (University of Kassel)

Title: Linear C3 - a novel probe to measure the 12C/13C ratio of the Galaxy

Abstract: Context. Carbon molecules and their 13C-isotopologues are commonly used to determine the 12C/13C abundance ratios in stellar and interstellar objects. In two previous SOFIA observation campaigns we successfully observed for the first time the 13C-substituted species 13CCC and C13CC. By comparing the derived column densities to those of the CCC main isotopologue we determined the 12C/13C ratio at the galactic of 20+/-4.2, which is in agreement with the value given by Belloche et al 2013. In addition, we observed an unexpected 13CCC/C13CC ratio of 1.2+/-0.1 which is much lower than the value of 2 expected for statistically formed isotopologues. We also found an anomaly of the P- and Q-branch transitions, that cannot be explained by current molecular spectroscopy. Further observations including higher J ro-vibrational transitions will give new insights into the formation process of 13C-carbon species and their spectroscopic properties. Aims. Our aim is to extend the data set of measured ro-vibrational transitions of 13CCC and C13CC to higher J-quantum numbers to derive more precise 13CCC and C13CC column densities and finally a more accurate 12C/13C isotope ratio. Methods. We propose to use the GREAT/upGREAT receiver on SOFIA to search for new ro-vibrational absorption lines of C13CC and 13CCC along the line of sight towards SgrB2(M). Excitation temperatures will be derived from the measured line intensities of C13CC. We chose appropriate settings which will include pairs of 13CCC and C13CC lines within a small frequency range. This will reduce the uncertainties of measured relative line intensities of the isotopologues and will significantly improve the accuracy of the 12C/13C abundance ratios. Synergies. The new results together with previously measured Q(2) and Q(4) transitions of 13CCC and C13CC will allow to derive a more accurate value of the 12C/13C ratio at the galactic center and give insights into isotopic shift effects caused by differences in the zero-point energy of the isotopologues. Anticipated results. We will perform a global data analysis of new and already available data of CCC, 13CCC and C13CC to derive accurate temperatures, column densities and isotopic shifts. We will discuss to what extend the pure carbon chain molecule is suited as a new sensitive probe to determine 12C/13C abundance ratios in carbon rich environments of the galaxy.

Proposal ID: 09_0191

Principal Investigator: Arshia Jacob (Max Planck Institute for Radio Astronomy; Bonn)

Title: To search for HeH+ in the He enriched compact HII region W3A

Abstract: Chemists have long been fascinated by the possible existence and formation of noble gas compounds since the synthesis of the first noble gas-bearing molecular ion- helium hydride, HeH+, (Hogness & Lunn~1925) in the laboratory by means of mass spectroscopy. The helium hydride cation is of immense importance in the chemistry of the early Universe, as it is one of the first molecules to be formed, opening a path to the production of molecular hydrogen right before the first stars are formed. Renewing interests in noble gas chemistry, the first successful detection of HeH+ made more recently toward the planetary nebula NGC~7027 by Guesten et al.(2019), using the upGREAT instrument on board SOFIA has encouraged several theoretical and laboratory studies to investigate the formation and destruction of HeH+ and its role in the formation of the first stars. Given, its importance in primordial chemistry we here, propose to extend the search for HeH+ in space through observations of the helium enriched layers of the W3 A region using upGREAT onboard SOFIA.

Proposal ID: 09_0194

Principal Investigator: Jordan Guerra (Villanova University)

Title: Mapping Large-scale Magnetic Fields in the Gould Belt

Abstract: The role of the magnetized turbulence in molecular clouds still remains an enigma in the study of star formation. It is suspected that magnetic fields and turbulence limit the rate at which stars form. A unique tool to study magnetic fields in these environments is the far-infrared dust (FIR) polarimetry. In particular, dust FIR polarimetric data from instruments such as HAWC+/SOFIA have allowed the study of magnetized turbulence at a unique resolution and statistics. We proposed a survey of polarimetric observations at 214 µm with HAWC+. The targets of these observations correspond to clouds in the Gould Belt -- a unique collection of star-forming regions close enough that the capabilities of HAWC+ will allow the resolution of meaningful physical scales. In particular, regions in a subset of clouds (Cepheus, Ophiucus, Orion, Perseus, and Taurus) are selected to complement other existing surveys. We will utilize maps of physical variables (e.g., mass density) from the Herschel Gould Belt Survey and molecular tracers such as ammonia (gas turbulence) from the Green Bank Telescope Ammonia Survey, along with the proposed observations to construct maps of magnetic field strength in each target. These maps can be compared to numerical simulations and provide observational constraints for models of molecular clouds.

Proposal ID: 09_0195

Principal Investigator: Snezana Stanimirovic (University of Wisconsin Madison)

Title: Thermal Pressure of the Perseus Molecular Cloud via Velocity Resolved [CII]

Abstract: We propose to use the upGREAT instrument on-board SOFIA to observe 158 micron [CII] and 63 micron [OI] emission in the direction of 5 radio continuum sources behind the Perseus molecular cloud. The [CII] observations, with existing neutral hydrogen (HI) observations, will constrain thermal pressure and volume density of the HI envelope around Perseus and test several theories for the formation of giant molecular clouds (GMCs). The constrained volume density will directly test the hypothesis that molecular clouds form from thermally-unstable HI gas. In conjunction with existing OH observations, we will test how reliable [CII] is a tracer of the "CO-dark" molecular gas for young GMCs which still have a large reservoir of HI and lack massive star formation. The thermal pressure measurements will also uniquely test the thermal balance and structure of the Perseus HI envelope, an environment where significantly more narrow pressure distribution is expected relative to random areas of the interstellar medium.

Proposal ID: 09_0197

Principal Investigator: John Carr (University of Maryland College Park)

Title: Water as Evidence of Surface Accretion in Protoplanetary Disks

Abstract: Disk accretion is fundamental to the formation of stars and planets, yet the physical mechanism that drives it is uncertain and remains a long-standing challenge. Recent observations of the Class I source GV Tau N reveal kinematic evidence for inflow in its disk atmosphere, at a rate comparable to T Tauri stellar accretion rates, providing support for the theoretical idea of disk accretion via "surface accretion" flows. We aim to find and study other examples of this phenomenon. We will use EXES to search for evidence of surface accretion flows (warm, redshifted water absorption at high column density) in the disk atmospheres of two Class I sources that show redshifted absorption in CO fundamental lines. A demonstration of the presence of high column densities of warm H 2 O absorption, at the same radial velocity as the redshifted CO absorption, will indicate that the inflowing molecular gas arises in the atmosphere of the inner disk. This will be provide observational support for surface accretion flows as a disk accretion mechanism in protoplanetary disks.

Proposal ID: 09_0198

Principal Investigator: Cody Lamarche (University of Toledo)

Title: Securing Far-Infrared Metal Abundances in NGC 6946

Abstract: Elements heavier than helium contribute less than one percent to the total mass of the local Universe, yet they significantly affect the way in which stars and galaxies form and evolve. Therefore, understanding the chemical enrichment history of the Universe is an essential part of understanding galaxy evolution. The ground-state fine-structure levels of the abundant metals oxygen and nitrogen, accessible to SOFIA in the far-infrared, will play a major role in uncovering this history. With the ability to penetrate the significant dust columns present in galaxies during the peak epoch of cosmic star formation, and little sensitivity to the unknown temperature structure of ionized nebulae that has plagued traditional optical strong-line metal-abundances for decades, FIR abundances offer many powerful advantages. Yet substantial work is still needed locally before these FIR methods can be extended to high-redshift galaxies. We propose a program to study NGC 6946, a bright, metal-rich, nearby spiral galaxy, targeting 8 HII regions that will be observed in concert with the ongoing CHAOS program on the LBT -- the largest, deepest survey of direct spectroscopic optical auroral-line metal-abundances ever undertaken in the local Universe. Combining SOFIA/FIFI-LS with CHAOS spectroscopy, archival Herschel/PACS and Spitzer/IRS, and VLA free-free continuum observations of the targeted HII regions in NGC 6946, we will explore several interrelated temperature-insensitive infrared abundance tools, including direct [OIII] abundances normalized to hydrogen using recombination or free-free emission, and expand and validate the novel O3N3 pure FIR-line abundance diagnostic. Our ancillary data also include deep optical IFU spectral mapping data, which bridge the resolution divide between the SOFIA and ground-based optical surveys.

Proposal ID: 09_0200

Principal Investigator: Arielle Moullet (SOFIA)

Title: Searching for water vapor in Main Belt Asteroids

Abstract: To date, the only water vapor detection on Main Belt Asteroids was obtained for Ceres, and displayed a great degree of temporal variability suggestive of sporadic production. We propose to observe the H182O transition at 547 GHz with GREAT on a sample of 5 Main Belt Asteroids displaying evidence or hints of water ice presence, including Ceres and Themis. The results will provide the most stringent set of constraints on water vapor production on asteroids. In addition to possibly confirm the presence of water within the current snowline, which has implications on the sources' formation location, the results will be interpreted in relation to the possible the water vapor production and loss mechanisms.

Proposal ID: 09_0201

Principal Investigator: C. Darren Dowell (JPL)

Title: Magnetic Field Structure of the Grand-Design Spiral Galaxy M51

Abstract: We propose a deep HAWC+ polarization map of the grand-design spiral galaxy M51, following up very successful exploratory HAWC+ observations of M51 and other nearby, IR-bright galaxies within the past three years. Far-IR polarimetry has now been demonstrated to be a powerful technique for tracing the magnetic field in the neutral medium of other dusty galaxies. In M51 (at the current depth) and NGC 1068, the field closely follows the spiral arms, but provides hints of underlying substructure. In this proposal, we plan to integrate 2 times deeper, which should produce an unprecedented polarization map of long-term value with several hundred resolution elements. We will use this map to test models of the formation of spiral arms, spurs, and magnetic fields themselves.

Proposal ID: 09_0203

Principal Investigator: Riwaj Pokhrel (University of Toledo)

Title: Impact of the magnetic field in the Mon R2 hub-filament system

Abstract: The magnetic field morphology and its role in hub-filament systems of molecular clouds is poorly constrained observationally. Understanding the field in such systems is crucial for understanding the formation of star clusters and massive stars. Recent observations of hub-filament systems have uncovered gas velocities consistent with the scenario that filaments feed material to the central proto-cluster hub and its massive (and less massive) stars. We will observe the plane-of-sky polarization pseudo-vectors on one of the best-known prototypical hub-filament systems in the Mon R2 giant molecular cloud using HAWC+ polarimeter at 214 µm. From these observations, we will infer the plane-of-sky magnetic field orientation a spatial resolution of ~0.07 pc in the radiating low line-mass filaments and in the massive central hub, probing very different environments within the same system. We will investigate the role of magnetic fields in forming massive stars and star clusters in these distinct environments. We will explore how the magnetic fields may facilitate gas flow from filamentary networks into the hub, the regulation of cluster formation by the magnetic field, estimate magnetic field energy densities in both environments, and and compare the results to observations of other high-mass star-forming regions, and both theoretical MHD simulations and models for different field configurations.

Proposal ID: 09_0210

Principal Investigator: Lars Bonne (Laboratoire d'Astrophysique de Bordeaux)

Title: Evidence from H2 emission of a cloud-cloud collision responsible for initiating high-mass star formation

Abstract: Studying the physical process(es) responsible for the formation of dense star forming gas in the multiphase interstellar medium (ISM) is a central topic to advance our understanding of the ISM evolution, in particular for the regions that form high-mass stars as their feedback drives the evolution of the ISM. Several models propose that shock compression, as a result of purely turbulent motions or large scale organised collisions, are essential to form this dense gas. CO observations towards the DR21 ridge, which is one of the most nearby high-mass star forming regions, suggest that this ridge has been formed as a result of a molecular cloud collision. Observing emission from the shock due to this collision would confirm this scenario of dense gas formation for the DR21 ridge. Because of the high collision velocity > 10 km/s and high preshock H2 density > 2000 cm^{-3} for the collision in this region, the molecular hydrogen 0-0S(1) transition at 17.035 micron will be sufficiently bright to be detected with EXES. Furthermore, the line intensity of this transition will allow to differentiate between excitation due to FUV irradiation and shock excitation, since models of both processes predict an order of magnitude difference for the line intensity. Important and new for this study, is that EXES has the spectral resolution to demonstrate whether the shock excitation is truly associated with the cloud-cloud collision. The proposed observations will thus allow to obtain a first undubitable detection of gas heated by a shock due to a cloud-cloud collision which triggers the formation of dense gas that forms high-mass stars.

Proposal ID: 09_0211

Principal Investigator: Archana Soam (SOFIA)

Title: INSPIRE: INvestigating Spatially varying temperatures in PDRs from pure rotational excItation of moleculaR hydrogEn

Abstract: Photodissociation Regions (PDRs) are important laboratories for interstellar medium (ISM) chemical and thermal effects. A large number of observational studies and several modeling codes have been dedicated to understanding these regions. However, their small-scale structures are still poorly constrained. While evidence points towards clumpy density and thermal structure, such variations are usually not taken into account in their analysis. Slit spectroscopy of the pure rotational lines of molecular hydrogen provides a unique probe of the small-scale variations of the thermal structure in PDRs. Earlier SOFIA/EXES long-slit observations of the S(1) and S(5) lines of H_2 in the reflection nebula IC 63 show temperature gradients along the slit, and across the PDR ridge, and when compared to ISO observations, consistent with the temperature variations being due to the level of UV illumination of the gas. Is this the case of IC 63 only, or do all PDRs behave the same way? We propose to use the EXES high-medium long (24”) slit mode to observe the H_2 v=0 J=3-1 and J=7-5 lines (S(1) and S(5)) across the most intense H_2 emission ridge in five reflection nebulae/PDRs. We will measure the gas temperature along the EXES slit in two near-by locations for each nebula, to quantify the spatial variations of temperature depending upon location, illuminating radiation, and distance from the illuminating source. The two position have been chosen to probe the fully illuminated gas ("Sunny" locations) and gas immediately behind the ridge ("Shady" location). These observations will provide a statistically significant number of PDRs to arrive at meaningful general conclusions on the temperature and its variations. We also propose to observe the H_2 v=0 J=2-0 line (S(0)) in the brightest PDR (rho Oph), to test if the 'two temperature structure' seen by Thi et al. (2009) in IC 63, using ISO-SWS observations, originates from the mixing of different regions in their large aperture, or whether two such phases can indeed be fully mixed, which might point to a significant role for formation-heating of some of the H_2 molecules.

Proposal ID: 09_0212

Principal Investigator: Jessica Agarwal (Technische Universitaet Braunschweig)

Title: Spatial and temporal variability of dust properties in comet 67P/Churyumov-Gerasimenko

Abstract: We propose to study the thermal emission by dust in the coma of comet 67P/Churyumov-Gerasimenko. Thanks to the European Space Agency's Rosetta mission, 67P is probably the best studied comet in the solar system. But connecting the Rosetta measurement obtained inside a few hundred km to Earth-based telescope observations sensitive to spatial scales beyond 1000 km remains an open challenge. The goal of this proposal is to characterise the size distribution, composition, and orientation of dust as a function of distance from the nucleus and of time while the comet approaches and recedes from perihelion. The spatial and temporal variability will help us to assess the different physical processes involved in the evo lution of comet dust between the inner and the outer coma. This will allow us to infer on dust properties as it leaves the nucleus and is least processed compared to the material incorporated into the comet during planetesimal formation. We propose to image the cometary coma at a resolution of about 1000 km at wavelengths of 7.7, 25.3, and 31.5 micron using SOFIA/FORCAST, during 4 nights at about monthly intervals for 3.5h per night. We will derive the spatially resolved colour temperature, and constrain the local dust particle size through comparison with numerical simulations of light scattering and thermal emission by dust aggregates. The observing conditions during Cycle 9 will be ideal, as the comet will be in the Northern night sky during the whole cycle, and will approach Earth to within 0.4 astronomical units, corresponding to a spatial resolution of about 360 km/arcsec. The next similar observing opportunity will be 13 years later. We expect strong synergies with the vast data set from the Rosetta mission and with ground-based telescope observations carried out during the mission.

Proposal ID: 09_0215

Principal Investigator: Thushara Pillai (Boston University)

Title: Study of Interstellar Magnetic Polarization: a Legacy Investigation of FIlaments (SIMPLIFI)

Abstract: Our understanding of star formation has been revolutionized by the insight that star-forming cores and hubs are embedded in complex filamentary networks that penetrate molecular clouds. Filaments differ greatly in their mass-to-length ratio -- which indicates the likelihood of star-forming fragmentation -- and the levels of associated star formation. Still, the exact role of filaments in star formation remains unclear. In particular, magnetic fields might play an important role, as indicated by well-ordered polarized dust emission that imply strong magnetic fields. Here we propose SIMPLIFI, a SOFIA HAWC+ Legacy program that will carry out the first large-scale study of the magnetic polarization of filaments. The sample covers a wide range of mass-to-length ratios and star formation activities, in order to probe representative conditions for star formation. SIMPLIFI includes local filaments which are starless or are forming low-mass stars. SOFIA will resolve the column density and magnetic structure of filament ridges and cores much more clearly than previous work with Planck. SIMPLIFI also targets distant filaments that form clusters and massive stars, to reveal differences between regions of high-mass and and low-mass star formation. Our project brings together an international team of observers, instrumentalists, and theorists to exploit these data to the fullest. This enables us to go beyond the standard Davis-Chandrasekhar-Fermi analysis, e.g. by using sophisticated flux-freezing models and complex numerical MHD simulations. A further unique feature of SIMPLIFI is our access to comprehensive imaging of gas density distributions and dynamics from dust and line observations. This enables SIMPLIFI to constrain the relative role of self-gravity, turbulence, and magnetic fields in star formation. SIMPLIFI will clarify the role of magnetic fields in star-forming filaments, and will provide a framework to "simplify" the diversity of filament properties.

Proposal ID: 09_0216

Principal Investigator: Matthew Hankins (Arkansas Tech University)

Title: Uncovering Sites of Isolated Star Formation in the Galactic Center with SOFIA/FORCAST

Abstract: Star formation in the Galactic Center (GC) occurs at an astonishingly low rate compared to the solar neighborhood despite containing a majority of the Galaxy's dense molecular gas. Resolving this pervading mystery has major implications for our understanding of star formation in other galactic nuclei, luminous infrared galaxies, and high redshift galaxies at the epoch of peak star formation. One of the more unusual aspects of star formation in the GC is the presence of a significant population of massive field stars which may have formed in relative isolation. In this program, we are proposing to obtain infrared imaging observations with SOFIA/FORCAST at 25 and 37 microns to study a sample of isolated mid-IR sources, many which also have far-IR counterparts and may be sites of ongoing star formation. This program is highly complementary to earlier observations from the FORCAST Galactic Center Legacy Survey from SOFIA cycle 7, which largely focused on bright, crowded regions near Sgr A, B, and C. In contrast, our proposed cycle 9 observations target relatively isolated sources, over half of which are at negative galactic latitudes which were poorly sampled by the Legacy Program. Our primary targets of interest are badly saturated in Spitzer/MIPS 24 micron observations and SOFIA/FORCAST is without a doubt the best facility to investigate these poorly studied objects to determine their true nature. Completing this proposed program will significantly enhance our understanding of star formation at the Galactic Center by filling in gaps in the mid-IR coverage of the region, and we will work with SMO to release any data obtained as part of this program as a supplement to the earlier FORCAST observations. Last, we note that this program has strong synergies with JWST, and will aid in source selection and observation planning for future mid-IR spectroscopic studies of sources in the GC.

Proposal ID: 09_0217

Principal Investigator: Veena VS (University of Cologne)

Title: Probing [CII] Emission Towards the Unusual Molecular Bubble G18.88-0.02

Abstract: BC_018.88-0.09 is a 60 pc filamentary infrared dark cloud in the Milky Way. Towards the center of the filament, there exists a 11 pc cavity G18.88-0.02 enclosed by high density molecular gas along the periphery. Energetics of this bubble/cavity point towards a massive stellar wind origin for the cavity despite the lack of typical signatures of high mass star formation activity such as the presence of HII regions and diffuse mid-infrared emission. Intermediate to late B type stars with negligible radio emission but significant emission in the far ultraviolet to form photodissociation regions (PDRs) could be responsible for such bubbles/cavities. These could be an important, but under-appreciated feedback mechanism in star formation. Thus, G18.88-0.02 serves as an excellent target to investigate the non-conventional feedback/cloud destruction mechanisms that are not identifiable with traditional star formation indicators.The [CII] fine structure line at 157.7 micron serves as an ideal tool to probe the emission from PDR associated with the cavity. This will shed light on the effect of intermediate/late B stars on the evolution and star formation activity of their parental clouds. The proposed observations using GREAT on board SOFIA will play a key role in understanding the role of such quiescent bubbles in the Galactic eco system.

Proposal ID: 09_0220

Principal Investigator: Raghvendra Sahai (JPL)

Title: Shocked and Scorched: A GREAT Investigation of [CII] and [OI] emission from free-floating Evaporating Gas Globules in the W5 Massive Star Formation Region

Abstract: We propose GREAT observations of the [CII]158 micron and [OI] 63 micron emission towards 3 select members of a new class of tadpole-shaped free-floating evaporating gas globules (frEGGs) in the W5 massive star-formation region (MSFR). Since the discovery of the most prominent member of this class in an HST imaging survey, we have now identified a substantial population of such objects in several MSFRs using Spitzer IRAC 8 micron images. By virtue of their distinct, isolated morphologies, frEGGs are ideal astrophysical laboratories for probing star-formation in irradiated environments. Molecular-line observations reveal the presence of dense molecular cores associated with these objects, with masses in the range ~0.5-10 Msun, and radio continuum imaging reveals bright photo-ionized peripheries around these objects. The ratio of the mass in the photodissociation region (PDR) surrounding the molecular gas can help constrain (a) the evolution of the frEGGs and the total time available for accretion by the star or stars that may form inside it, and (b) their mass function. The line profiles will be used to probe the photoevaporative flow that is expected to drive frEGG evolution. We will use sophisticated 3-D numerical simulations of dynamical and chemical evolution of frEGGS to reproduce our SOFIA data and additional existing multiwavelength data on frEGGs. The proposed study will allow us to probe the effects of a less energetic external environment on star-formation in irradiated molecular cores by comparison with archival observations of 3 frEGGs in the Cygnus MSFR. We discovered photo-evaporative outflows and found the mass of atomic gas to be a small fraction of the total mass budget in these frEGGs, implying that they are relatively young. This study will pave the way for a larger SOFIA survey of frEGGs, leading to new insights into the complex star formation process in UV-irradiated environments.

Proposal ID: 09_0221

Principal Investigator: Ming Sun (University of Alabama in Huntsville)

Title: [C II] in the cluster galaxies undergoing ram pressure stripping

Abstract: Ram pressure stripping (RPS) is an important process in galaxy evolution. Recent multi-wavelength data have revealed many examples of galaxies undergoing RPS, often accompanied with multi-phase tails. As energy transfer in multi-phase medium is an outstanding question in astrophysics, important for e.g., galaxy formation and AGN feedback, RPS galaxies provide great examples to address the significant questions in multi-phase medium and star formation. [C II] has been established as an important tracer of the cold gas and star formation. However, there has not been a systematical study for the [C II] emission from RPS galaxies (especially their tails). On the other hand, we do know that [C II] emission can be enhanced by additional pressure from shocks, turbulence and collisional heating, which is ubiquitous in RPS galaxies. We propose SOFIA/FIFI-LS observations on five galaxies in the Coma cluster and A1367 for the first sample study for the [C II] emission from galaxies undergoing strong RPS. The [C II] data will be combined with the FIR, CO and Halpha data for multi-wavelength diagnostics and study. We will examine whether [C II] emission is enhanced in galaxies undergoing strong RPS and search for [C II] emission in the tails. [O I] from galaxies is also expected to provide additional constraints. We emphasize that the proposed science can only be done by SOFIA now and has never been tried before. Luckily, this is still within SOFIA's reach!

Proposal ID: 09_0227

Principal Investigator: Jose Pablo Fonfria (IFF-CSIC)

Title: The chemical interdependence of CO2 and H2O in O-rich evolved stars

Abstract: Evolved stars are known to be surrounded by a circumstellar envelope (CSE) composed of matter ejected by the star in the form of molecular gas and dust. The molecular species that can be found in these environments depend on the initial abundance ratio C/O of this ejected matter. The most chemically active are the stars where C/O>1 (C-rich) followed by those with C/O<1 (O-rich) while S-type stars (C/O~1) are not very chemically active. Two of the most abundant molecular species formed in the vicinity of the central stars of O-rich CSEs are H2O and CO2. Observing the thermal emission of any of these molecules from the ground have been always challenging due to atmospheric opacity and only with space observatories such as ISO, Spitzer or Herschel (only for H2O) it has been possible. This is true in particular for CO2, which does not have a pure rotational spectrum in the mm domain. It is believed that the abundances of CO2 and H2O are tightly related as both seem to form from OH. Nevertheless, the lack of observations, mostly of CO2, has prevented us to properly constrain the chemical models that aim to explain the abundances of these important molecules. But the recent observations of CO2 lines toward R Leo and RX Boo at 14 and 16um carried out with SOFIA/EXES have demonstrated that it is not necessary to launch a space observatory to observe the spectrum of this molecule. Therefore, we propose to observe 10 evolved stars with SOFIA/EXES at 14 or 16µm and 7.5µm to analyze and to correlate the spectra of H2O and CO2 in every star of the list. The region when they formed, their abundances, and the relation between them will be derived to help constrain the chemical models of CSEs of O-rich evolved stars.

Proposal ID: 09_0231

Principal Investigator: Alexandre Lazarian (University of Wisconsin Madison)

Title: Testing a new method for identifying regions of gravitational collapse within a magnetized molecular cloud using HAWC+ and GBT/ARGUS

Abstract: Understanding how star formation is regulated requires studying the energy balance between turbulence, magnetic fields, feedback and gravity within molecular clouds. Here we propose to use HAWC+ to test a promising new method for both (a) identifying regions within clouds that are gravitationally collapsing, and (b) characterizing the relative importance of magnetic fields, turbulence and self-gravity within clouds. This method is based on predictions from the Velocity Gradient Technique (VGT), that in collapsing regions of molecular clouds the spatial velocity gradients will rotate by 90deg to align parallel to the magnetic field. Such rotations mark the transition from a magnetic field and turbulence dominated regime at low densities, to higher density regions that are collapsing under gravity. VGT rotations towards high density clumps have been observed in simulations and in low resolution (10' FWHM) comparisons between Planck inferred magnetic field maps and velocity gradients derived from molecular line observations. However Planck cannot resolve magnetic fields within dense gas clumps and filaments. Here we propose to make high resolution (19'' FWHM) HAWC+ Band E polarization observations of the nearby dense clump L1551 that shows a change in velocity gradient orientation with respect to the magnetic field at Planck resolution. We also request GBT/ARGUS spectral line observations of HCN and HCO+ to make VGT maps at the same resolution as our HAWC+ data. With these data we will (1) determine whether the rotations of velocity gradients to align parallel with the magnetic field predicted by the VGT method do exist, (2) use the VGT to identify the boundary of the self-gravitating region within L1551, and (3) determine the transition density, which will allow us to estimate the magnetic field strength of L1551. Validation of this VGT technique with HAWC+ observations would provide a powerful new tool for studying gas dynamics in star formation.

Proposal ID: 09_0233

Principal Investigator: Amanda Townsend (University of California Davis)

Title: Taking Betelgeuse’s Temperature -- Placing unique EXES observations to investigate the cause of the Great Dimming of 2019/2020 in context

Abstract: Betelgeuse's naked-eye-visible dimming has captured the attention of the public and astronomers alike. While there are two leading hypotheses to explain the cause -- circumstellar dust, and a drop in the star's effective temperature-- there is no conclusive evidence in favor of either one. While there are observations that support both ideas, no conclusive evidence exists in favor of either one. During the Great Dimming of 2019/2020, where Betelgeuse decreased significantly in optical brightness, SOFIA-EXES obtained observations of Betelgeuse at two different mid-infrared wavelength locations: [Fe II] 25.99 µm and [S I] 25.25 µm. New, complementary follow-up observations to this pre-existing data will allow us to discriminate between the two ideas. The EXES Great Dimming observations match previous pre-dimming observations of the iron and sulfur emission lines, respectively, from 2015 and 2017. This unique mid-infrared dataset also shows photospheric water absorption features which are sensitive to temperature. Along with follow-up observations of Betelgeuse, we propose to observe a set of template M-supergiant stars with different temperatures at these same wavelengths in order to fully contextualize the relationship between these water lines and the star's photospheric temperature using theoretical models. This will allow us to determine Betelgeuse's effective temperature during the Great Dimming and assess whether this played a role in the star's observed behavior.