S18A0125

Clusters of galaxies are statistical objects by nature, and investigating these systems over cosmic times will require a large sample at each cosmic epoch and that free from selection biases as much as possible. With such motivations, we have been conducting a hybrid cluster search program with HSC on Subaru called HSC-HSC, which can not only search for passively evolving red sequence galaxies with broad-band colours but also line emitting star forming galaxies with narrow-band filters. During the course of this survey, we have identified the new class of objects, namely, blue-dominated young clusters without developed red-sequence. In this proposal, as a pilot spectroscopic follow-up program, we aim to confirm 3 such systems at z=0.84 with FOCAS as well as 3 normal dual (blue+red) clusters for comparison, and investigate the properties of galaxies therein such as star formation rates, metallicities and ionization states. This study will unveil the intrinsic scatter of cluster/galaxy properties depending on the evolutionary phases of clusters even at the same cosmic times which is crucial to understand the cosmic histories of cluster assembly and evolution and how star-forming activities are quenched in clusters.


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