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- Title
Do blue galaxy-clusters have hot intracluster gas?
- Authors
Misato, Rana; Toba, Yoshiki; Ota, Naomi; Yamamoto, Naoaki; Kodama, Tadayuki; Okabe, Nobuhiro; Oguri, Masamune; Mitsuishi, Ikuyuki
- Abstract
We present herein a systematic X-ray analysis of blue galaxy clusters at z = 0.84 discovered by the Subaru telescope. The sample consisted of 43 clusters identified by combining red-sequence and blue-cloud surveys, covering a wide range of emitter fractions (i.e. 0.3–0.8). The spatial extent of the over-density region of emitter galaxies was approximately 1 Mpc in radius. The average cluster mass was estimated as 0.6(<1.5) × 1014 M ⊙ from the stacked weak-lensing measurement. We analyzed the XMM-Newton archival data, and measured the X-ray luminosity of the hot intracluster medium. As a result, diffuse X-ray emission was marginally detected in 14 clusters, yielding an average luminosity of 5 × 1042 erg s−1. To the contrary, it was not significant in 29 clusters. The blue clusters were significantly fainter than the red-dominated clusters, and the X-ray luminosity did not show any meaningful correlation either with emitter fraction or richness. The X-ray surface brightness was low, but the amount of gas mass was estimated to be comparable to that observed in the 1013–1014 M ⊙ cluster. Based on the results, we suggest that the blue clusters are at the early formation stage, and the gas is yet to be compressed and heated up to produce appreciable X-rays. Follow-up spectroscopic measurements are essential to clarify the dynamical status and co-evolution of galaxies and hot gas in the blue clusters.
- Subjects
GALAXY clusters; X-rays; GASES
- Publication
Publications of the Astronomical Society of Japan, 2022, Vol 74, Issue 2, p398
- ISSN
0004-6264
- Publication type
Article
- DOI
10.1093/pasj/psac002