Photodissociation Regions and the Carbon Cycle Across Galactic Environmnets

Photodissociation regions (PDRs) are the sites where the atomic-to-molecular transition occurs, as well as the transition between the three phases of carbon (C+, C and CO) known as the "carbon cycle". The abundances and the emission of the carbon cycle depend strongly on the environmental conditions of the ISM including the cosmic-ray ionization rate, the FUV intensity and the gas-phase metallicity. Of particular interest is that the abundances of carbon and oxygen are enriched differentially by stellar nucleosynthesis and the overall galactic chemical evolution, having an impact on the carbon cycle emission. These emission lines are frequently used to estimate the environmental parameters, which ultimately shape the density distribution of the interstellar gas in galaxies. Through three-dimensional numerical modelling and comparison with observational data, I will discuss how each of the aforementioned line emissions can be used as a diagnostic of the chemical state of the interstellar medium. I will also discuss the utility of [CII] 158um and [CI](1-0) lines as alternative H2-gas tracers for both diffuse and dense gas of low C/O ratios.

Thomas Bisbas (Zhejiang Lab)
Lile Wang
Thursday, November 2, 2023 - 3:30PM to Thursday, November 2, 2023 - 4:30PM
Thomas Bisbas obtained his degree of Physics from the Aristotle University of Thessaloniki (Greece) and his PhD degree from Cardiff University (UK). He has been a postdoctoral researcher in various institutions including the University College London, Max Planck fur Extraterrestriche Physik, and University of Florida. He has been a DFG Fellow at the University of Cologne. He is currently a Principal Investigator at Zhejiang Lab in Hangzhou and has received the Qianjiang Friendship Award (钱江友谊奖). His research interest includes numerical modelling of the interstellar medium and photodissociation regions, radiative transfer, and star-formation with a particular focus on extragalactic studies. He is the author of several algorithms including 3D-PDR and PDFchem.