Colloquium on Oct. 29, 2020

Metallicity dependence of molecular gas in self-regulating interstellar medium: H2, CO, and the CO-dark gas

Speaker: Chia-Yu Hu (MPI)

Venue: Video Conference

Time: 15:00 PM, Thursday, Oct. 29, 2020

Abstract:

Stars form in cold and dense gas predominately composed of molecular hydrogen (H2). As H2 is invisible in typical conditions, carbon monoxide (CO) is the most widely used tracer for H2 observationally. The relation between H2 and CO is expected to be different at low metallicities. However, the interstellar medium (ISM) at low metallicities are still poorly understood. I will present recent hydrodynamical simulations coupled with a time-dependent chemistry network that model the ISM under the self-regulation of stellar feedback across different metallicities. I will demonstrate the non-equilibrium effect of chemistry leads to a significant change in the HI/H2 transition but less so for the C/CO transition. As a result, the amount of CO-dark gas, contrary to conventional wisdom, does not increase much as metallicity decreases.