NOAO >   Observing Info >   Approved Programs >   2002A-0092

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Proposal Information for 2002A-0092


PI: Sandhya Rao, University of Pittsburgh, rao@everest.phyast.pitt.edu
Address: 3941 O'Hara Street, Pittsburgh, PA 15260, USA

CoI: David Turnshek, University of Pittsburgh
CoI: Daniel Nestor, University of Pittsburgh
CoI: Eric Monier, Ohio State University
CoI: Wendy Lane, Naval Research Laboratory

Title: Galaxies Associated with Damped and Sub-Damped Ly(alpha) Systems

Abstract: We are assembling optical-IR photometric (UBRIJHK) data on galaxies in the fields of 36 QSOs whose absorption spectra indicate that the sight-lines toward them pass through 40 large columns of neutral hydrogen gas with N_HI>10^19 atoms cm^-2. About 43% (17) of the absorption systems are confirmed damped Ly(alpha) (DLA) systems with N_HI\ge2\times10^20 atoms cm^-2, while the remainder are sub-DLA with 10^19<N_HI<2\times10^20 atoms cm^-2. These systems all have z<1 and \it HST UV spectroscopy gives their HI column densities. Our specific goal is to use multi-color images of these fields to derive photometric redshifts for all the galaxies down to the limit L~0.05-0.1L^*. For each absorption system we will then determine which galaxy is the absorbing galaxy. Further measurements will determine the absorbing galaxies' impact parameters, luminosities, and, when possible, morphological types. We have already assembled a substantial part of this data set and, from our work over the last several years, know that almost all of the DLA galaxies are (unexpectedly) much fainter than L^*. Consequently, the most straightforward and efficient way to make substantial future progress is by employing the photometric redshift technique. This work has important significance since it will allow us to determine the nature of the extragalactic objects that contain the bulk of the neutral gas mass in the Universe at z<1. This is a continuation of the recently approved program 2001A-0323.


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