Assigned ID: 690 ----- Attempting Submission 1 (Fri Feb 25 21:53:09 GMT 2011) ----- Damped Lya Absorbers (DLAs) are the highest column density systems seen in the spectra of distant quasars. Some DLAs are thought to represent absorption from gas associated with an intervening galaxy disks, halo, tidal tail, etc., along the line of sight and DLAs are a key method of studying star formation, metal abundances, and kinematics at high redshift. These systems are exceedingly rare at low-z where the intervening galaxies can be studied in detail, so the precise nature of these important diagnostics remains poorly-understood. However, there is one DLA present along every extragalactic sight line which we can study in exhaustive detail: the Milky Way DLA! We propose a study of sight lines through the Galactic DLA using archival far-UV spectra from STIS, COS, and GHRS. We will construct 30-40 full-DLA profiles for the Milky Way DLA by combining the absorption spectra of pairs of nearly-antipodal sight lines (within ~20 degrees of antipodal). This will allow us to sample a realistic distribution of physical conditions in a system exhibiting realistic kinematics. Our DLA profiles will intersect the Galaxy at a range of angles and probe a variety of Galactic structures - high-velocity clouds, tidal tails, possible outflows, etc. - the same features which are inferred but rarely confirmed in some external DLAs. This diversity of sight lines through the same galaxy will let us determine if the wide range of observed properties in external DLAs (column density, velocity dispersion, abundances, etc.) could be an effect of the precise details of the line of sight or is inherent to the population of DLA hosts.

QUASAR ABSORPTION LINES AND IGM 12 Medium false 0.0 0.0 false false false false SUPPORTED