AR 14293 (Archival Research)

Sun Jul 14 19:50:09 GMT 2024

Principal Investigator: Claude-Andre Faucher-Giguere
PI Institution: Northwestern University
Investigators (xml)

Title: Metallicity and Azimuthal Angle Diagnostics of Inflows and Outflows: Interpreting HST Measurements of Circum-Galactic Gas Flows
Cycle: 23

Galaxies do not grow in sync with their dark matter halos, the stellar masses of galaxies being typically more than one order of magnitude below the cosmic baryon fraction. The regulation of galaxy growth occurs in the circum-galactic medium (CGM), where gas accretion from the cosmic web and galactic outflows interact with one another. Major progress in probing inflows and outflows observationally has been enabled by HST/COS, which has uncovered evidence for a bi-modality in the metallicity distribution of Lyman limit systems (LLSs) associated with CGM gas. The low- and high-metallicity branches have tentatively been identified with inflows and outflows, respectively, but this interpretation remains uncertain because no published simulation has reproduced the observed bi-modality. Complementary measurements using HST imaging have revealed a bi-modality in the azimuthal angle distribution of strong Mg II absorbers relative to the disk of star-forming galaxies. The azimuthal angle bi-modality has also tentatively been interpreted as a way to separate inflows and outflows. We will use a new suite of ultra-high resolution cosmological simulations with resolved ISM physics and stellar feedback, combined with radiative transfer, to study the physical nature of CGM absorbers. By tracking the history of gas elements in our simulations, we will quantify the association of absorbers of different metallicity and azimuthal angle with inflows, outflows, and stripping processes, and develop long-sought diagnostics of inflows and outflows. We will directly compare mock absorption spectra from our simulations to COS data and make several key predictions testable over the next few years.