Speaker
Description
The latest ALMA and JWST observations provide new information on the formation
and evolution of galaxies in the early Universe, 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. Due to its low excitation potential, [C II] emission can be
produced in photodissociation regions, neutral atomic gas and molecular clouds. To
properly capture the cold-gas processes taking place in such environments (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. In this way, we are able to accurately
track the evolution of H I, H II and H$_2$ in a cosmological context and predict the
contribution of each gas phase to high-redshift [C II] luminosities. We also show
how [C II] luminosities correlate with SFR and stellar mass of the hosting galaxy,
and how these relations evolve with redshift. Moreover, we probe the correlation
between [C II] luminosity and molecular gas mass and 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 the molecular budget at
primordial epochs.
