Discovery of a Dwarf Post-Starburst Galaxy Near a High Column Density Ly-alpha Absorber

Abstract

We report the discovery of a dwarf (M_B = -13.9) post-starburst galaxy coincident in recession velocity (within uncertainties) with the highest column density absorber (N_HI = 10^15.85 cm^{-2} at cz = 1586 km/s) in the 3C~273 sightline. This galaxy is by far the closest galaxy to this absorber, projected just 71 kpc on the sky from the sightline. The mean properties of the stellar populations in this galaxy are consistent with a massive starburst ~3.5 Gyrs ago, whose attendant supernovae, we argue, could have driven sufficient gas from this galaxy to explain the nearby absorber. Beyond the proximity on the sky and in recession velocity, the further evidence in favor of this conclusion includes both a match in the metallicities of absorber and galaxy, and the fact that the absorber has an overabundance of Si/C, suggesting recent type II supernova enrichment. Thus, this galaxy and its ejecta are the expected intermediate stage in the fading dwarf evolutionary sequence envisioned by Babul & Rees to explain the abundance of faint blue galaxies at intermediate redshifts.Comment: 33 pages, 4 figures, ApJ in pres