Contributed Talk - Splinter ISM

Thursday, 24 September 2020, 10:08   (virtual room F)

PDR diagnostics across galactic environments

Thomas G. Bisbas, Jonathan C. Tan, Kei E.I. Tanaka
University of Cologne

We present three-dimensional astrochemical simulations and synthetic observations of magnetised, turbulent, self-gravitating molecular clouds. We apply these models to explore various galactic interstellar medium (ISM) environments, including cosmic-ray ionization rates in the range of ζcr=1e-17 -- 1e-14 s-1, far-UV intensities in the range of Go=1 -- 100 and metallicities in the range of Z=0.1 -- 2 Zo. The simulations also probe a range of densities and levels of turbulence, including cases where the gas has undergone recent compression due to cloud-cloud collisions. In particular, we examine: i) the column densities of carbon species across the cycle of CII, CI and CO, along with OI, in relation to the HI-to-H2 transition; ii) the velocity-integrated emission of [CII] 158μm, [CI] 609μm and 370μm, [OI] 63μm and 146μm, and of the first ten 12CO rotational transitions; iii) the corresponding Spectral Line Energy Distributions; iv) the usage of the most important of the aforementioned lines to describe the dynamical state of the clouds; v) the behavior of the most commonly used ratios between transitions of CO and [CI]; and vi) the conversion factors for using CO and CI as H2-gas tracers. In the era of ALMA, SOFIA and the forthcoming CCAT-prime telescope, our results can be used to understand better the behaviour of systems in a wide range of environments, including close to the Galactic Center, starburst galaxies and systems in the high-redshift Universe.