GLIMPSE (Galactic Legacy Infrared Mid-Plane Survey Extraordinaire)

GLIMPSE is Spitzer Legacy project, that delivers data to the Spitzer Science Center (SSC). The GLIMPSE I (aka GLIMPSEI), GLIMPSE II (aka GLIMPSEII), GLIMPSE 3D (aka GLIMPSE3D), GLIMPSE360, Vela-Carina, DeepGLIMPSE, SMOG, and Cygnus-X deliveries all contain a "Catalog" and an "Archive", all are served through IRSA's General Catalog Query Tool, Gator. The GLIMPSEI source lists are from the 20070412 "FINAL" (DR5) data delivery; the GLIMPSEII source lists are from the "final" data delivery on 20080418 and the December 2008 and November 2009 single epoch catalog deliveries; the GLIMPSE3D source lists are concatinated from five deliveries dates: 20070717, 20080130, 20080721, 20090106, 20091102. GLIMPSEI, GLIMPSEII and GLIMPSE3D images are served through IRSA's general search service Atlas.

GLIMPSEI

The GLIMPSEI Catalog and Archive contain sources for the entire GLIMPSEI Survey (l=10-65 deg, 295-350 deg, b=+- 1 deg) plus the Observation Strategy Validation (OSV) region at about l=284 deg. The SSC pipeline version used for the GLIMPSEI v2.0 source lists is mostly S13.2 (corrected for the jailbar effect), with an occasional re-observation processed with SSC pipeline version S14 or later.

NOTE: For source lists from l=10 to 11 and l=349 to 350 deg please select the GLIMPSEII dataset, not the GLIMPSEI dataset.

GLIMPSEII

The GLIMPSEII Catalog and Archive contain sources for the entire GLIMPSEII Survey region. The nominal GLIMPSEII Survey region is l= -10 deg to 10 deg (details in table below). These data products include all epochs of the GLIMPSE II survey region. They also include the Galactic center data from the General Observer (GO) program GALCEN (PI: Stolovy, Program ID=3677 search Spitzer Data at IRSA), as well as GLIMPSE I data at the boundary of the surveys (at l=10 deg and l=349 deg).

longitude (deg) latitude (deg)
5<l<10 and 350<l<355 -1<b<1
2<l<5 and 355<l<358 -1.5<b<1.5
0<l<2 and 358<l<360 -2<b<2

NOTE: For source lists from l=10 to 11 and l=349 to 350 deg please select the GLIMPSEII dataset, not the GLIMPSEI dataset.

GLIMPSE3D

GLIMPSE 3D Archive Notice: In June 2009, an error in IRSA's copy of the GLIMPSE 3D Archive was corrected. The affected sky coverage is l = 333-337 degrees; b = -1 to -3 degrees. 883,569 rows from the original Archive delivery were incorrectly excluded from the database, and replaced by 443,320 rows from the GLIMPSE 3D Catalog. This error affects users of the GLIMPSE 3D Archive prior to June 2009.

The GLIMPSE3D Catalog and Archive contain sources from five cumulative deliveries (DR1, DR2, DR3, January 2009, and November 2009 from 2007-2009) from GLIMPSE 3D. GLIMPSE3D adds vertical extensions, generally up to |b| < 3deg, but up to |b| < 4.2deg in the center of the Galaxy. The goal of this coverage is to provide data to study the vertical stellar and interstellar structure of the inner Galactic disk, bar, and spiral arms.

GLIMPSE360

The GLIMPSE360 Catalog and Archive contain sources from the three cumulative deliveries, covering Galactic longitudes l=65.0-265.0 deg., excluding l=102-109deg (SMOG) and l=76-82deg (Cygnus-X). Even though bands 3 & 4 are not used in the Spitzer Warm Mission, the fields are included in the GLIMPSE360 source lists, filled in by null values.

Vela-Carina

The Vela-Carina Catalog and Archive contain sources from longitudes l=255-295d.

DeepGLIMPSE

The DeepGLIMPSE Catalog and Archive contain sources from longitudes l=265-350d and l=25-65d. DeepGLIMPSE increases the dynamic range over GLIMPSE, GLIMPSE3D, and Vela-Carina by a factor of 13 on the faint end and a factor of 3 on the bright end. Approximately 43% of the DeepGLIMPSE observations are of areas not previously observed. Even though bands 3 & 4 are not used in the Spitzer Warm Mission, the fields are included in the GLIMPSE360 source lists, filled in by null values.

SMOG

The SMOG Catalog and Archive contain sources from longitudes l=102-109d.

Cygnus-X

The Cygnus-X Catalog and Archive contain sources from longitudes l=76-82d extracted from data processed using the GLIMPSE pipeline. The same data has also been processed by the Cygnus-X Legacy team.


Catalog vs Archive (More Reliable vs More Complete)

The Catalog is a more reliable list of sources, and the Archive is a more complete list both in number of sources and flux measurements at each wavelength (less nulling of fluxes). The main differences between the Catalog and Archive are 1) fluxes brighter than a threshold that marks a nonlinear regime are nulled (removed) in the Catalog; 2) sources within 2.0 arcsec of another are culled (removed) from the Catalog, whereas the Archive allows sources as close as 0.5 arcsec from another; 3) sources within the PSF profile of a saturated source are culled from the Catalog but not the Archive; and 4) the Catalog has higher signal-to-noise thresholds and slightly more stringent acceptance criteria (e.g., number of detections in various bands). The IRAC data were bandmerged with the 2MASS All-Sky Point Source Catalog. See the GLIMPSEI v2.0, GLIMPSEII v2.1, GLIMPSE3D v1.4, GLIMPSE360 v1.5, Vela-Carina v1.0, DeepGLIMPSE v1.3, SMOG v1.1, and Cygnus-X v1.0 documents from the Data Products Document Repository for more details. There are about 31.2 million sources in the GLIMPSEI Catalog and about 49.2 million in the GLIMPSEI Archive. There are about 19.1 million sources in the GLIMPSEII Catalog and about 24.4 million sources in the GLIMPSEII Archive. There are about 20.4 million sources in the GLIMPSE3D Catalog and about 32.2 million sources in the GLIMPSE3D Archive. There are about 42.6 million sources in the GLIMPSE360 Catalog and about 49.4 million sources in the GLIMPSE360 Archive. There are about 2 million sources in the Vela-Carina Catalog and about 4.5 million sources in the Vela-Carina Archive. There are about 38.2 million sources in the DeepGLIMPSE Catalog and about 63.5 million sources in the DeepGLIMPSE Archive. There are about 2.5 million sources in the SMOG Catalog and about 2.8 million sources in the SMOG Archive. There are about 3.9 million sources in the Cygnus-X Catalog and about 4.4 million in the Cygnus-X Archive.

Catalog and Archive Fields and Flags

Each entry in the GLIMPSE I, II, 3D, 360, Vela-Carina, DeepGLIMPSE, SMOG, and Cygnus-X Catalogs and Archives have the following information:


designation     -> SSTGLMC GLLL.llll±BB.bbbb, SSTGLMA GLLL.llll±BB.bbbb 
2MASS PSC names -> 2MASS designation, 2MASS counter 
position        -> l, b, dl, db, ra, dec, dra, ddec 
flux            -> magi, di_m, fi, dfi, rms_fi (IRAC); mag_t, dt_m, ft, df_t (2MASS) 
diagnostic      -> sky_i, sn_i, dens_i, # detections mi out of ni possible (IRAC); sn_t (2MASS) 
flags           -> Close Source Flag (csf), Source Quality Flag (sqf_i), Flux Method Flag (mfi) (IRAC);
                   Source Quality Flag (sqf_t) (2MASS)

where i is the IRAC wavelength number (IRAC bands 1 - 4) (3.6 µm, 4.5 µm, 5.8 µm and 8.0 µm) and t is the 2MASS wavelength bands (J, H, Ks).

Details of the fields are as follows. Note that IRSA's General and Basic Catalog Search Tools (Gator and BabyGator) calculate colors, using magnitude measurements in the GLIMPSE source lists. For more information on these Gator-derived columns, click here.

Designation

The 'designation' entry can have the following set of information:

  Archive=> SSTGLMA GLLL.llll+-BB.bbbb
  Catalog=> SSTGLMC GLLL.llll+-BB.bbbb
  

This is the object designation or name as specified by the IAU recommendations on source nomenclature. It is derived from the coordinates of the source, where G denotes Galactic coordinates, LLL.llll is the Galactic longitude in degrees, and ±BB.bbbb is the Galactic latitude in degrees. The coordinates are preceded by the acronym SSTGLMC (GLIMPSE Catalog) or SSTGLMA (GLIMPSE Archive). For Vela-Carina, the prefixes are SSTVELC and SSTVELA respectively. For DeepGLIMPSE, the prefixes are SSTGLMDPC and SSTGLMDPA respectively. For SMOG, the previxes are SSTSMOGC and SSTSMOGA respectively. For Cygnus-X, the prefixes are SSTCYGXC and SSTCYGXA respectively.

Designation is:

  SST = Spitzer Space Telescope
  GLM = GLIMPSEI, GLIMPSEII, GLIMPSE3D, or GLIMPSE360 projects or VEL = Vela-Carina project 
or GLMDP = DeepGLIMPSE project or SMOG = SMOG project or CYGX = Cygnus-X project A = more complete Archive C = highly reliable Catalog G = Galactic coordinates LLL.llll = Galactic longitude (degrees) of the source +-BB.bbbb = Galactic latitude (degrees) of the source

2MASS PSC information

The 2MASS designation is the source designation for objects in the 2MASS All-Sky Release Point Source Catalog. It is a sexagesimal, equatorial position-based source name of the form hhmmssss±ddmmsss, where hhmmssss is the right ascension (J2000) coordinate of the source in hours, minutes and seconds, and ±ddmmsss is the declination (degrees, minutes, seconds). The 2MASS counter is a unique identification number for the 2MASS PSC source.

Position

There are 8 'position' related fields:

         l, b, dl (error), db (error), ra, dec, dra (error), ddec (error)

The position is given in both Galactic (l,b) and equatorial (RA, Declination) J2000 coordinates, along with estimated uncertainties. The pointing accuracy is 1 arcsec (Werner et al. 2004). The SSC pipeline does pointing refinement of the images based on comparison with the 2MASS Point Source Catalog, whose absolute accuracy is typically <0.2 arcsec (Cutri et al. 2005). After applying the SSC geometric distortion corrections and updating to the 2MASS positions, the GLIMPSE point source accuracy is typically 0.3 arcsec absolute accuracy, limited by undersampling of the point-spread function. The position uncertainties are calculated by the bandmerger based on the uncertainties of individual detections, propagated through the calculation of the weighted mean position.

Fluxes

The following are 'flux' related fields:

         magi & mag_t, di_m & dt_m (error), fi & f_t, dfi & df_t (error), rms_fi

For each IRAC band i = 3.6, 4.5, 5.8, and 8.0 µm and, when available 2MASS band t = J, H, and Ks, the fluxes are expressed in magnitudes (magi, mag_t) and in mJy (fi, f_t). Each IRAC flux is the error-weighted average of all independent detections of a source. The 2MASS magnitudes and uncertainties are from the 2MASS All-Sky Release Point Source Catalog. They are the j_m, j_msigcom, h_m, h_msigcom, and k_m, k_msigcom columns from the 2MASS PSC. The zeropoints for converting from flux to magnitude for the S13.2 and later SSC processing versions are from Reach et al. (2005) for the IRAC bands and Cohen et al. (2003) for 2MASS and given in Table 1 below. Note, all the fluxes have the same zero points as they are on the same calibration (v2 GLIMPSEI & GLIMPSEII, GLIMPSE3D, GLIMPSE360, Vela-Carina, DeepGLIMPSE, SMOG, Cygnus-X).

Table 1. Zeropoints for Flux to Magnitude Conversion 

Band                        J      H      K      [3.6]    [4.5]    [5.8]    [8.0]
GLIMPSEI Zeropoints (Jy)   1594   1024   666.7   280.9    179.7    115.0    64.13

The IRAC flux/magnitude uncertainties (dim; dfi) are computed during the photometry stage and take into account photon noise, readnoise, goodness of flat fielding, and PSF fitting (Stetson 1987).

The rms deviation (rms_fi) of the individual detections from the final flux of each source is provided.

Diagnostics

The 'flux diagnostics' related fields are:

         sky_i, sn_i, sn_t, dens_i, # detections mi out of ni possible

The associated flux diagnostics are a local background level (sky_i) (i = 3.6, 4.5, 5.8, and 8.0 µm) in MJy/sr, a Signal/Noise (sn_i), a local source density (dens_i) (number of sources per square arcmin), and number of times (mi) a source was detected out of a calculated possible number (ni). The Signal/Noise is the flux (f_i) divided by the flux error (dfi). The Signal/Noise for the 2MASS fluxes (sn_t) have been taken from the 2MASS PSC (the j_snr, h_snr and k_snr columns). The local source density is measured as follows: The individual IRAC frame is divided into a 3×3 grid, each of the nine cells being 1.71 arcmin x 1.71 arcmin. A source density is calculated for each cell (number of sources per arcmin^2), and is assigned to each source in that cell. The local source density can be used to assess the confusion in a given region, along with the internal reliability. mi and ni can be used to estimate reliability. ni is calculated based on the areal coverage of each observed frame; due to overlaps some areas are observed more than twice per band.

Flags

There are three types of flags: the Close Source Flag, the Source Quality Flag and the Flux Calculation Method Flag. The Close Source Flag is set if there are Archive sources that are within 3 arcsec of the source. The Source Quality Flag provides a measure of the quality of the point source extraction and bandmerging. The Flux Calculation Method Flag describes how the final Catalog/Archive flux was determined.



REFERENCES

Cohen, M., Wheaton, W.A., and Megeath, S.T. 2003, AJ, 126, 1090

Cutri, R. et al. 2005

Reach, W. et al. 2005, PASP, 117, 978.

Stetson, P. 1987, PASP, 99, 191.

Werner et al. 2004, ApJS, 154, 1.