Study of the Galactic Photon Dominated Region in Rho Ophiuchus A

Abstract

Photon Dominated Regions(PDR) are predominantly neutral regions in the interstellar medium(ISM), which contains both atomic and molecular gas. Physical properties of the PDRs are governed primarily by far-ultraviolet photons from nearby stars, or the interstellar radiation field. PDRs provide a unique opportunity to study the effect of young massive stars on the interstellar gas.

In this project, we study the PDR near the active star forming region ρ Oph A. We have used new, velocity resolved [CII] observations, obtained with the Stratospheric Observatory For Infrared Astronomy (SOFIA), as the primary dataset. We also use observations in known PDR tracers, neutral oxygen(from Herschel Space Observatory archive) and PAH molecules(from Spitzer Space Telescope archive); as well as CO, from the archival data of James Clerk Maxwell Telescope(JCMT). Using these tracers, we study the structure and distribution of gas in the PDR.

We have used a numerical model for PDRs, the Meudon PDR code (Le Petit et al., 2006) to interpret the observed intensities of spectral lines to constrain the physical conditions (hydrogen number density (n(H)) and far-ultraviolet radiation strength) in ρ Oph A. We have also extensively used the PDR model to study, in general, the variation of intensities of major PDR tracers as a function of density, intensity of FUV radiation field and metalicity.