(Proposal ID) S12A-036

(PI) Toshikawa, Jun

(Proposal Title)
A First Site of Cluster Formation at z~6

(Abstract)
We propose to carry out spectroscopic observation with DEIMOS targeting for 43 
galaxies in/around the highest-redshift protocluster. In this protocluster, at 
least, eight galaxies are actually clustering at z=6.01 within the narrow 
redshift range of delta z < 0.05. Our preliminary study of the three-
dimensional structure of the protocluster revealed several subgroups on a 
large filamentary structure, suggesting that it is still on a very early stage 
of cluster formation and making larger cluster through merger. We would like 
to carry out a deeper and wider observation than previous one. This will 
result in a significant increase of the confirmed protocluster members and 
provide more accurate three-dimensional structure of the protocluster. The 
wide-field spectroscopy will also reveal the relation between protocluster in 
formation and its surrounding large-scale structure. We will also study the 
possible environmental effect in z~6 protocluster by comparing some 
quantities, such as mass and age derived from SED fitting, of protocluster-
members with those of field galaxies. Through the proposed observation, we can 
approach to the cluster formation history by looking at its primitive 
structure and the relation with large-scale structure.