Speaker
Description
It is known that the fraction of blue galaxies in galaxy clusters increases with increasing redshift, suggesting that star formation in the galaxy clusters has decayed rapidly over cosmic time (Butcher & Oemler 1984). Nearby groups of galaxies often show the anti-correlation between the blue fraction of member galaxies and their X-ray luminosities (Mulchaey 2003; Ota et al. 2004). However, whether or not this anti-correlation is applicable to distant galaxy clusters is still unclear. To understand the dependence of blue fraction on X-ray luminosity and co-evolution of galaxies and hot intracluster gas, we investigate the gas properties of the blue clusters. In this work, we present an analysis of XMM-Newton observations of 43 blue galaxy clusters at z = 0.84 discovered with the Hyper Suprime-Cam (HSC) on the Subaru Telescope. The sample is drawn from galaxy clusters selected with the Hybrid Search for Cluster with HSC (HSC-HSC) survey. Based on the HSC-HSC cluster catalog and XMM-Newton archival data, we estimate X-ray luminosities of 43 blue clusters. As a result, 13/43 clusters are detected by XMM-Newton, and their average X-ray luminosity is $L\rm{_x} (0.5\textit{-}2 \, \rm{keV}) = (6.8 \, \pm \, 0.7) \times 10^{42} \, \rm{erg} \, \rm{s}^{-1}$. Because AGNs exist in 7/43 clusters, their X-ray luminosities may be affected by AGN emission. We compare our results with those of red clusters and discuss the evolutionary stage of intracluster gas in the blue clusters.
