Date : The 17th of February, 2016 (Wed.)
Speaker : Dr. Ken Mawatari (Osaka-Sangyo University)
Title : Discovery of a new type DLA: HI absorber along a galaxy sight-line
We have performed a series of spectroscopic observations of
the LBGs and LAEs photometrically selected from the Subaru S
cam imaging of the SSA22 field. Especially the VLT VIMOS obs
ervations in 2008 yields the high S/N spectra which enables
us to investigate the intervening IGM HI absorptions. Using
normal galaxies as background light sources to map the Lya a
bsorption lines is a novel approach to study the intervening
HI absorbers. In my talk, we focus on a z=3.3 DLA identifie
d in a z=3.6 LBG sight-line. The DLA HI column density is as
high as log(N_HI) = 21.7. By measuring the residual flux in
the Lya trough we constrained the covering fraction of the
DLA gas cloud over the background LBG, resulting a f_cov>0.7
or DLA area > 1 kpc^2. We searched for a galaxy hosting the
DLA utilizing the deep multi-band images, resulting that th
ere is no counterpart galaxy with SFR > a few solar mass. Th
ese properties are consistent with the previous measurements
and theoretical predictions for QSO-DLAs. If the occurence
rate of gal-DLAs is similar to that if QSO-DLAs the sample n
umber of gal-DLAs will increase dramatically in the next dec
ade, which open a new window in examining the DLA size and c
ounterpart galaxies. I also plan to introduce our new survey
, HIT, to investigate the HI absorption systems.

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