Affiliation: Max Planck Institute for Astrophysics

Contribution: Oral

Title: COLDSim: A new look at H2, H I and H II in cosmological simulations.

Abstract: The latest ALMA and JWST observations provide new information on the formation and evolution of galaxies at the Epoch of Reionization. Of particular importance are measurements of the molecular gas budget of these z>5 objects, which is known to be the main fuel for star formation. A powerful tool for measuring the gas content in galaxies at the Epoch of Reionization is the [C II] emission line, originated in photodissociation regions, neutral atomic gas and molecular clouds. To properly capture the cold-gas processes (molecule formation, self-shielding, dust grain catalysis, photoelectric and cosmic-ray heating), we introduce a new set of state-of-the-art hydrodynamic simulations (COLDSim) including time-dependent non-equilibrium chemistry, star formation, stellar evolution, metal spreading and feedback mechanisms. We are able to accurately track the evolution of H I, H II and H_2 in a cosmological context and to predict the contribution of each gas phase to high-redshift [C II] luminosities. We show that although H I is the dominant gas phase contributing to the [C II] emission, this transition is still a powerful tool to constrain the mass of H_2. Finally, we provide theoretical values for the conversion factor α_[CII] from z=6 to z=12. These physically-motivated predictions can be used in observational works to infer not only the total cold gas budget in primordial epochs but also its partition into molecular and atomic neutral state.

This contribution can be found here (pdf).