(Proposal ID) S10A-036

(PI) Kassin, Susan

(Proposal Title)
MOIRCS Multi-PA Kinematics of Galaxies at z~2+: A Search for Disks

(Abstract)
Massive galaxies undergo their most rapid growth in stellar mass during the 
epoch from 1 ~< z ~< 2.5, but their kinematic state over this period is 
unknown. Understanding this will provide crucial insight into whether galaxies 
are indeed assembling at z ~ 2, or if they are already together and simply 
settling to disks. Previous attempts at determining the kinematics of galaxies 
at z ~ 2 have been limited by single slits or small samples of objects with 2D 
kinematics. We will address this by measuring robust kinematics for ~ 50 
galaxies with multi-band Hubble imaging at 2.1 < z < 2.7 using the unique 
capabilities of Subaru/MOIRCS. Kinematics will be measured at 3 position 
angles (PA). Combining information from each PA will reveal the existence, or 
lack of, disk-like kinematics. The MOS capabilities of MOIRCS, along with our 
multi-position angle strategy, will allow reliable characterizations of 
kinematics at least 4 times more efficiently than other methods. A comparable 
survey of 50 galaxies with a single slit or an IFU would take 25 or 17 nights, 
respectively, neglecting all overheads. The proposed observations will result 
in the largest most definitive census of the kinematic state of baryons when 
the Universe was likely entering its most rapid phase of growth.