(Proposal ID) S15B-172

(PI) Suzuki, Nao

(Proposal Title)
Mapping z~2 Large-Scale Structure with 3D Lyman-alpha Forest Tomography

(Abstract)
The Lyman-alpha forest absorption in the spectra of background sightlines 
traces the dark-matter density field at z>2. With a dense grid of background 
sightlines, it is possible to generate a full 3D map of the IGM absorption. 
We propose using Keck/LRIS-B to obtain spectra of faint QSOs and LBGs with 
g_{AB} ~24 within the COSMOS field that have typical transverse separations 
of 3 Mpc/h allowing a 3D reconstruction on similar scales. This program is a 
continuation of an earlier program that experienced heavy weather loss, but 
the limited data we obtained seems promising and has already resulted in a 
published paper. We request additional time to complete our original program, 
which will allow us to further investigate a possible protocluster/Zeldovich 
pancake which was seen in the preliminary data. This program is a pathfinder 
for the large-volume tomographic mapping that will be carried out by the 
Subaru Prime-Focus Spectrograph. We anticipate the study of the tomography 
of the universe would become one of the major fields of astrophysics in the 
era of TMT.