Unmasking Damped Lya Absorbing Galaxies
Hsiao-Wen Chen (MIT)
I will present current results from searching for galaxies giving rise
to damped DLA absorbers (DLAs) at z<1. Using 14 galaxies that are
known to produce DLA features in the spectra of background QSOs, I
will show that intermediate-redshift galaxies possess large HI
envelope out to 24-30 h^{-1} kpc radius. In addition, the photometric
and spectral properties of these galaxies confirm that DLA galaxies
are drawn from the typical field population, and not from a separate
population of low surface brightness or dwarf galaxies. Comparisons
of the ISM abundances of the DLA galaxies and the metallicities of the
absorbers at large galactic radii suggest that some DLAs originate in
the relatively unevolved outskirts of galactic disks. An abundance
profile characterized by a radial gradient of -0.041+/-0.012 dex per
kiloparsec (or equivalently a scale length of 10.6 h^{-1} kpc) is
found from galactic center to 30 h^{-1} kpc radius based on an
ensemble of six galaxy-DLA pairs. Finally adopting this abundance
gradient and known N(HI) profiles of nearby galaxies, I will show that
the on-average low metal content of the DLA population can arise
naturally as a combination of gas cross-section selection and
metallicity gradients commonly observed in local disk galaxies.
