A Shot in the Dark: A Technique for Locating the Stellar Counterparts of Damped Lyα Absorbers

We present initial results from a Magellan telescope program to image galaxies that give rise to damped Lyα absorbers (DLAs) at 1.63<=z_DLA<=2.37. Our program differs from previous efforts in that we target quasars with intervening Lyman limit systems (LLSs) along the line of sight at redshift z_LLS>3.5. The higher redshift LLS is applied as a blocking filter to remove the glare of the background quasar at the rest-frame ultraviolet wavelengths of the foreground galaxy. The complete absence of quasar light offers us an unimpeded view along the sight line to the redshift of the LLS, allowing for an exhaustive search of the DLA galaxy to the sensitivity limit of the imaging data (at or better than 0.25L_*). In both of our pilot fields (PKS 2000-330 [z_DLA=2.033] and SDSS 0322-0558 [z_DLA=1.69]), we identify an L_* galaxy within 5" of the sight line that has optical colors consistent with star-forming galaxies at z~2. We examine the correlation between absorption-line properties and galaxy luminosity and impact distance, and we compare the high-redshift galaxy and absorber pairs with those known at z<1.

Observations reported here were obtained at the Magellan telescopes, a collaboration between the Observatories of the Carnegie Institution of Washington, the University of Arizona, Harvard University, the University of Michigan, and the Massachusetts Institute of Technology.