SZ and X-ray combined analysis of a distant galaxy cluster, RX J2228+2037

Free access article

Issue		A&A Volume 387, Number 1, May III 2002


Page(s)		56 - 62
Section		Extragalactic astronomy
DOI		http://dx.doi.org/10.1051/0004-6361:20020394

A&A 387, 56-62 (2002)
DOI: 10.1051/0004-6361:20020394

SZ and X-ray combined analysis of a distant galaxy cluster, RX J2228+2037

E. Pointecouteau^{1, 2}, M. Hattori², D. Neumann³, E. Komatsu⁴, H. Matsuo⁵, N. Kuno⁶ and H. Böhringer⁷

¹ CESR-CNRS, 9 Av. du Colonel Roche, 31028 Toulouse, France
² Astronomical Institute, Tohoku University, Sendai 980-8578, Japan
³ SAp-CEA, L'Orme des Merisiers, 91191 Gif-sur-Yvette Cedex, France
⁴ Department of Astrophysical Sciences, Princeton, NJ 08544, USA
⁵ National Astronomical Observatory, Mitaka Tokyo 181-8588, Japan
⁶ Nobeyama Radio Observatory, Minamimaki Nagano 384-1305, Japan
⁷ Max-Planck Institut Für Extraterrische Physik, Garching 85740, Germany

( Received 14 December 2001 / Accepted 4 March 2002 )

Abstract
We have performed a combined analysis of X-ray and Sunyaev-Zel'dovich data in the direction of the distant galaxy cluster, RX J2228+2037. Fitting a $\beta$ -model to the high-resolution HRI data gives $r_{\rm c} = 103 \pm 12\, h_{70}^{-1}$ kpc and $\beta=0.54 \pm 0.03$ . The dependency of the Sunyaev-Zel'dovich effect with respect to the gas temperature allows us, through the additional use of the 21 GHz data of the cluster, to determine $k_{\rm B} T_{\rm e}=10.4 \pm 1.8\, h_{70}^{1/2}$ keV. Extrapolating the gas density profile out to the virial radius ( $R_{\rm v}=r_{178}=2.9$ Mpc), we derived a gas mass of $M_{\rm g}(r<R_{\rm v})= (4.0\pm 0.2)\times 10^{14}\, h_{70}^{-5/2}\,{M}_\odot$ . Within the hypothesis of hydrostatic equilibrium, the corresponding extrapolated total mass for this source is: $M_{\rm tot}(r<R_{\rm v})=(1.8 \pm 0.4)\times 10^{15}\, h^{-1}\,{M}_\odot$ , which corresponds to a gas fraction of $f_{\rm gas}=0.22\pm 0.06\, h_{70}^{-3/2}$ . Our results on the temperature and on the cluster mass classify RX J2228+2037 among the distant, hot and very massive galaxy clusters. Our work highlights the power of the association of galaxy cluster mapping observations in X-ray and the SZ effect to derive the cluster's physical properties, even without X-ray spectroscopy.

Key words: cosmology: observation -- galaxies: clusters: individual: RX J2228+2037 -- galaxies: intergalactic medium

Offprint request: E. Pointecouteau, etienne@astr.tohoku.ac.jp

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