(Proposal ID) S17A-064

(PI) Shimakawa, Rhythm

(Proposal Title)
Deep [O ii] line imaging in a H i overdense region at z=5

(Abstract)
This proposal aims to find [OII] emitters (O2Es) at z=4.8 with narrow-band 
(BrG) imaging on the MOIRCS. The target is a part of the dense HI large-scale 
structure (LSS) at z=4.8 inferred from Ly alpha forest of the lensed galaxy, 
A1689-7.1 at z=4.866 in Abell1689. The HI flux transmission at z=4.69--4.84 is 
only ~30% of the average value at the same redshift, which suggests that HI 
overdensity extends at least ~80 comoving Mpc along the line of sight. 
The target would provide us with great opportunity to study galaxy formations 
within baryonic LSS at z=5. With this motivation, we carried out Ly alpha 
emitter (LAE) survey at z=4.7--4.9 with two NB filters on the Suprime-cam, 
and then find a LSS associating with inferred HI overdense region. However, 
we know that it is important to find galaxies by method other than Ly alpha 
selection since Ly alpha selection should be influenced by Ly alpha depletion 
by HI and dust absorption. To resolve this issue, deep NB imaging of [OII] 
line should be powerful to robustly select star-forming galaxies associating 
with dense HI structure. Because of the lensing magnification, we expect that 
[OII] line fluxes are magnified by 0.5--5.0 mag. Thus, the target field should 
be the best laboratory to test the effectiveness of high-z O2E search at the 
start.