(Proposal ID) S14B-112

(PI) Koyama Yusei

(Proposal Title)
 MOIRCS follow-up spectroscopy of an extremely rich galaxy cluster at z=1.52

(Abstract)
With our recent broad-band and narrow-band(Halpha) imaging survey with Suprime-
Cam/MOIRCS, we discovered a strong over-density of galaxies around a radio 
galaxy at z=1.52 (4C,65.22). The highest-density region (cluster core) is 
clearly dominated by red-sequence galaxies, while the Halpha-selected star-
forming (SF) galaxies are preferentially located in the outskirt region. This 
spatial segregation resembles like lower-z clusters, suggesting the newly 
discovered structure is a well-matured system. We here propose extensive 
MOIRCS follow-up spectroscopy of this interesting field to confirm their 
physical association and to investigate the spectral properties of individual 
gaiaxies. Our science goals are: (1) to map 3-D dynamics of member galaxies 
and measure the cluster total mass to examine the evolution of cluster mass-
normalised SFR (SigmaSFR/M_{cl}), (2) to study the environmental effects on 
the mass--metallicity relation at z=1.5 by using [NII]/Halpha ratio, (3) to 
test environmental impacts on the excitation properties of inter-stellar 
medium (ISM) within the galaxies via [OIII]/Halpha ratio, and (4) by devoting 
some of our slits on the red-sequence galaxies, we will test if the red 
galaxies dominating cluster core are really completely quiescent, or if they 
exhibit any signature of residual SF or nuclear activity.