GALEX DISCOVERY OF A DAMPED Ly{alpha} SYSTEM AT REDSHIFT z {approx} 1

Abstract

We report the first discovery of a QSO damped Ly{alpha} system (DLA) by the Galaxy Evolution Explorer (GALEX) satellite. The system was initially identified as an Mg II absorption-line system (z {sub abs} = 1.028) in the spectrum of Sloan Digital Sky Survey (SDSS) QSO J0203-0910 (z {sub em} = 1.58). The presence of unusually strong absorption due to metal lines of Zn II, Cr II, Mn II, and Fe II clearly suggested that it might be a DLA with N {sub HI} {>=} 2 x 10{sup 20} atoms cm{sup -2}. Follow-up GALEX NUV grism spectroscopy confirms that the system exhibits a DLA absorption line, with a measured H I column density of N {sub HI} = 1.50 {+-} 0.45 x 10{sup 21} atoms cm{sup -2}. By combining the GALEX N {sub HI} determination with the SDSS spectrum measurements of unsaturated metal-line absorption due to Zn II, which is generally not depleted onto grains, we find that the system's neutral-gas-phase metal abundance is [Zn/H] = -0.70 {+-} 0.22, or {approx}20% solar. By way of comparison, although this system has one of the largest Zn{sup +} column densities, its metal abundances are comparable to other DLAs at z {approx} 1. Measurementsmore » of the abundances of Cr, Fe, and Mn help to further pin down the evolutionary state of the absorber.« less