(Proposal ID) S12A-056

(PI) Toshikawa, Jun

(Proposal Title)
Searching for Protoclusters at z~6

(Abstract)
Protoclusters in the early universe would provide a great deal of information 
on the primordial conditions at their birth; however it is difficult to 
discover them due to very low number density. In our previous study, we have 
discovered a protocluster z~6 by using a combination of i'-dropout technique 
and unique wide-field imaging capability of SuprimeCam. This is the highest-
redshift clustering structure ever observed. We propose to take GMOS 
spectroscopy for two other plausible protocluster candidates at z~6, that are 
discovered in the CFHTLS Deep fields with more than 4sigma overdense 
significance. First of all, we would like to definitely confirm that our 
target regions are real protoclusters. The number density of protocluster 
based on wide field survey allows us a direct comparison with CDM model, which 
gives constraints of the cosmological parameters. We can qualitatively 
characterize the general properties of early structures at z~6 and its 
possible environmental effects at highest redshift end. The comparison of 
cluster size and velocity dispersion with those of low redshift will trace 
the cluster formation in a virialization process. From the proposed 
observation, we would like to statistically discuss nature of cluster 
formation and galaxy formation in these primitive structures.