Oral Presentation
Mapping galaxies with various populations in proto-supercluster at z=2.23 with QSO clustering
Presenter: Ko Ishida (Tohoku University)
Galaxy clusters form and develop at intersections of filamentary large scale structures (LSSs) over cosmic times. It is strongly suggested that the formation and evolution of galaxies and their super massive black holes are tightly related to the surrounding environment, likely due to the enhanced galaxy mergers and vigorous gas accretion along filaments. Since the star formation activities in the progenitors of present-day clusters are thought to be peaked at z~2, it is the critical epoch for us to witness the structure growth and galaxy evolution in action.
In this study, we focus on a unique structure at z=2.23 hosting proto-clusters and their surrunding LSSs, called 2QZ cluster field. This is first identified by a strong clustering of 4 QSOs at similar redshifts within a 30x30 cMpc region, which provides us a unique laboratory to investigate the effect of QSOs to the surrounding environments. Previous multi-wavelength observations have revealed the existence of LSSs traced by Hα emitters (HAEs), dusty starburst galaxies, and X-ray point sources (likely AGNs). In order to better cover the entire structure with suppressed bias, we performed a new analysis utilizing the archival imaging data taken with HSC on Subaru and WFCAM on UKIRT. To sample galaxies with various stellar populations, in addition to the improved HAE selection, we newly apply the gzK color selection, which is sensitive to both quiescent and star forming galaxies. We can also estimate stellar mass, star formation rate, and clustering properties. As a result, we have discovered new overdensities traced by gzK galaxies which are likely connecting between the previously known structures, which allow us to make a more detailed comparison of galaxy properties as a function of local/global environments as well as QSO proximity. We note that this redshift is also unique as there is a narrow-band filter on HSC/Subaru which captures redshifted Lyα emitters across the entire structures, which will tell us HI gas distribution if combined with the existing Hα map, and thus gas accumulation and QSO feedback processes.
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