(Proposal ID) S11A-075

(PI) Onodera, Masato

(Proposal Title)
Mapping the Highest Concentrations of Passive Galaxies at z>1.4

(Abstract)
The best tracers of the highest density peaks in the large scale structure are 
passive ellipticals, but for z~>1.4 existing surveys are missing this crucial 
population. Given the successful detection of spectral features of passive 
galaxies at z > 1.4 in our previous runs (S09A-043 and S10A-058), we propose 
to continue exploiting MOIRCS to observe over the COSMOS field ~ 35 bright 
passively evolving galaxies at 1.4 < z < 2.5. We shall obtain their accurate 
redshifts, locate them in their LSS environment, derive stellar masses and 
ages, physical sizes, and constrain their velocity dispersion. Our primary 
scientific goals are: * Map the highest density peaks at z ~ 2, in particular 
confirm the nature of bound groups/clusters for the redshift spikes found in 
previous runs; * Calibrate the photometric redshifts for passive galaxies at 
z > 1.4, thus using them to map the emergence of quenched galaxies in this 
critical redshift interval; and * Measure the stellar velocity dispersion 
(sigma) of the galaxies with the highest S/N ratio, checking for the existence 
of galaxies with extremely high sigma's, and quantifying the proportion of 
superdense and normal ellipticals at these redshifts. We shall target the 3 
most populous concentrations of such galaxies within each field of view of 
MOIRCS.