(Proposal ID) S11A-144

(PI) Inada, Naohisa

(Proposal Title)
The Direct Size Measurement of Damped Lyalpha Systems through Lensed Quasars

(Abstract)
We are proposing the current largest systematic observation to measure the 
typical size of damped Ly alpha systems (DLAs). Although DLAs are very 
important object as the largest neutral gas reservoirs in the Universe, very 
little is still known about their physical properties. Lensed quasar samples 
is an ideal tool to measure the (transverse) size and/or geometry of DLAs, 
because we can observe a single absorber (DLA) through more than one sight-
line using lensed quasar images. Here, we propose to measure the typical 
transverse sizes of DLAs from systematic spectroscopy of the lensed quasars 
in the SDSS Quasar Lens Search (SQLS). The variety of image separations of the 
SQLS lenses enable us to investigate how much a difference of DLA absorption 
lines (or Mg ii and/or Fe ii absorption lines for lower redshift DLAs) among 
more than one sight-lines changes according to the lensing image separations. 
The difference would be expected to increase suddenly at the typical transverse
 size of DLAs. In addition, the wide range of source quasar redshifts of the 
SQLS lenses will give us a chance to see the redshift evolution of DLAs. We 
also measure the redshifts of the lensing galaxies to solve each lensing 
geometry; this makes the SQLS lenses a much better cosmological probe.