Universal profiles of the intracluster medium from Suzaku X-ray and Subaru weak-lensing observations

Nobuhiro Okabe, Keiichi Umetsu, Takayuki Tamura, Yutaka Fujita, Motokazu Takizawa, Yu Ying Zhang, Kyoko Matsushita, Takashi Hamana, Yasushi Fukazawa, Toshifumi Futamase, Madoka Kawaharada, Satoshi Miyazaki, Yukiko Mochizuki, Kazuhiro Nakazawa, Takaya Ohashi, Naomi Ota, Toru Sasaki, Kosuke Sato, Sutieng Tam

Research output: Contribution to journalArticlepeer-review

6 Citations (Scopus)


We conduct a joint X-ray and weak-lensing study of four relaxed galaxy clusters (Hydra A, A 478, A 1689, and A 1835) observed by both Suzaku and Subaru out to virial radii, with the aim of understanding recently discovered unexpected features of the intraclustermedium (ICM) in cluster outskirts. We show that the average hydrostatic-to-lensing total mass ratio for the four clusters decreases from ∼70% to ∼40% as the overdensity contrast decreases from 500 to the virial value. The average gas mass fraction from lensing total mass estimates increases with cluster radius and agrees with the cosmicmean baryon fraction within the virial radius, whereas the X-ray-based gas fraction considerably exceeds the cosmic values due to underestimation of the hydrostatic mass. We also develop a new advanced method for determining normalized cluster radial profiles for multiple X-ray observables by simultaneously taking into account both their radial dependence and multivariate scaling relations with weak-lensing masses. Although the four clusters span a range of halo mass, concentration, X-ray luminosity, and redshift, we find that the gas entropy, pressure, temperature, and density profiles are all remarkably self-similar when scaled with the weak-lensing M200 mass and r200 radius. The entropy monotonically increases out to ∼0.5 r200 ∼r1000 following the accretion shock heating model K(r) ∝ r1.1, and flattens at ≳0.5 r200. The universality of the scaled entropy profiles indicates that the thermalization mechanism over the entire cluster region (> 0.1 r200) is controlled by gravitation in a common way for all clusters, although the heating efficiency in the outskirts needs to be modified from the standard r1.1 law. The bivariate scaling functions of the gas density and temperature reveal that the flattening of the outskirts entropy profile is caused by the steepening of the temperature, rather than the flattening of the gas density.

Original languageEnglish
JournalPublications of the Astronomical Society of Japan
Issue number5
Publication statusPublished - 2014 Oct 1


  • Galaxies: clusters: individual (Hydra A, Abell 478, Abell 1689, Abell 1835)
  • Gravitational lensing: weak
  • X-rays: galaxies: clusters

ASJC Scopus subject areas

  • Astronomy and Astrophysics
  • Space and Planetary Science


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