Stars on Double Duty: Probing Cool Gas in Galaxies at Z ∼ 0.6 with Stellar Light

University of California Observatories, University of California, Santa Cruz, CA 95064, USA
e-mail: This email address is being protected from spambots. You need JavaScript enabled to view it.

Abstract

The luminous components of galaxies can act as powerful probes of halo gas in foreground galaxies along the sightline. We use Keck/LRIS absorption-line spectroscopy of a luminous, blue background galaxy at z = 0.69 to study Mg II halo gas in the outskirts (ρ = 11.1h⁻¹kpc) of a massive, poststarburst galaxy in the foreground at z = 0.47. The foreground absorber shows signs of recent merger activity and is host to a low-luminosity AGN. The halo absorption we observe is extremely strong (W_r(2796) = 4.0 ± 0.1Å) and is indicative of a large Mg II gas velocity width (> 400kms⁻¹). We briefly discuss the possible origins of this absorption, including multiphase cooling of hot halo gas and galactic winds/outflows.