My name is Jun Toshikawa. I am a JSPS postdoctoral fellow, working at Institute for Cosmic Ray Research (ICRR), the University of Tokyo. The primary goal of my research is revealing and studying the growth history of galaxy clusters. How galaxies are assembling into galaxy clusters, located at the nodes of the cosmic web? When do galaxies in these highest density peaks differ from those in fields? To address these questions, it is necessary to directly reveal the evolutionary steps of galaxy clusters through the observation of their progenitors, "protoclusters", across cosmic time.
In our previous researches, we have discovered a protocluster at z=6.01 in the Subaru Deep Field by the combination of dropout technique and follow-up spectroscopy (press release). The above pictures show the Subaru telescope (left) and the central region of the z=6.01 protocluster (right). We have also conducted a protocluster search from z~3 to z~6 in the CFHT Legacy Survey Deep Fields and confirmed some protoclusters.
We are now expanding this protocluster search into the extremely wide-field survey of Hyper SprimeCam (HSC) mounted on Subaru telescope. We will, for the first time, be able to obtain the systematic sample of protoclusters at z~2-6 by the HSC survey (initial results). We would like to address the open questions of large-scale structure formation and environmental effects on galaxy evolution by the synergy between the systematic sample constructed by Subaru telescope and the unique follow-up capabilities of other telescopes — e.g., VLT, Keck, HST, ALMA and JWST in the future.