Study of the S1 PDR in Rho Ophiuchi: A GREAT/SOFIA View

Photodissociation Regions (PDRs) are manifestations of the influence of massive stars on their environment and provide us with important clues to the role of these stars in the formation of a new generation of stars. The Rho Ophiuchi dark cloud complex located at a distance of 138pc, harbors a large number of newly formed stars as well as the reflection nebula associated with the early B star S1. We studied the PDR associated with S1 using [C II] 158 micron observations with GREAT/SOFIA obtained from the SOFIA data archives. This data set was complemented with maps of CO(3-2), 13CO(3-2), and C18O(3-2), observed as a part of the James Clerk Maxwell Telescope (JCMT) Gould Belt Survey, with archival HCO+(4-3) JCMT data, as well as with [O I] 63 and 145 micron imaging with Herschel/PACS. We analyzed the sources of far-ultraviolet (FUV) radiation illuminating the S1 PDR and made an accurate estimate of the spectral type of the highly extincted star S1. We compared the [C II] emission both morphologically and kinematically with the dedicated molecular and PDR tracers to conclude that the PDR consists of a diffuse extended region (n~3000-5000 cm^-3) with high density clumps (n>10^5 cm^-3) embedded in them. In this talk I will present this analysis, which is published in Mookerjea, Sandell, Vacca et al (2018) A&A, 616, A31. I will then discuss the results of our subsequent observations of the radio continuum emission from the ionized gas as well as HI emission at 21 cm using the Giant Metrewave Radio Telescope (GMRT), which provide an improved overview of the origin of the [C II] emission in the S1 PDR.