XMM-Newton observation of the distant () galaxy cluster RX J1120.1+4318

¹ CEA/DSM/DAPNIA, Service d'Astrophysique, L'Orme des Merisiers, Bât. 709, 91191 Gif-sur-Yvette, France
² Science Payloads Technology Divn., Research and Science Support Dept., European Space Agency, ESTEC, Keplerlaan 1, Postbus 299, 2200AG Noordwijk, The Netherlands
³ Institut d'Astrophysique Spatiale, Université Paris-Sud, 91405 Orsay Cedex, France
⁴ Laboratoire d'astrophysique de l'Observatoire Midi-Pyrénées, UMR5572, CNRS, UPS, 14 Av. E. Belin, 31400 Toulouse, France
⁵ Centre d'Etude Spatiale des Rayonnements, 9 avenue du colonel Roche, BP 4346, 31028 Toulouse, France
⁶ Harvard-Smithsonian Center for Astrophysics, 60 Garden Street, Cambridge, MA 02138, USA
⁷ Astrophysics Research Institute, Liverpool John Moores University, Twelve Quays House, Egerton Wharf, Birkenhead L41 1LD, UK
⁸ European Space Agency, Research and Scientific Support Division, ESTEC, Postbus 299 Keplerlaan 1, 2200AG Noordwijk, The Netherlands
⁹ Present adress: University of Alabama in Huntsville, Physics Department, OB 201B Huntsville, AL 35899, USA
¹⁰ Physics Department, Carnegie Mellon University, 5000 Forbes Avenue, Pittsburgh, PA15213, USA

Corresponding author: M. Arnaud, marnaud@discovery.saclay.cea.fr

Received: 3 April 2002
Accepted: 24 April 2002

Abstract

We report on a 20 ks XMM observation of the distant cluster , discovered at in the SHARC survey. The cluster has a regular spherical morphology, suggesting it is in a relaxed state. The combined fit of the EPIC/MOS&pn camera gives a cluster mean temperature of with an iron abundance of . The temperature profile, measured for the first time at such a redshift, is consistent with an isothermal atmosphere up to half the virial radius. The surface brightness profile, measured nearly up to the virial radius, is well fitted by a , with and a core radius of . We compared the properties of  with the properties of nearby clusters for two cosmological models: an Einstein–de Sitter Universe and a flat low density Universe with . For both models, the scaled emission measure profile beyond the core, the gas mass fraction and luminosity are consistent with the expectations of the self-similar model of cluster formation, although a slightly better agreement is obtained for a low density Universe. There is no evidence of a central cooling flow, in spite of the apparent relaxed state of the cluster. This is consistent with its estimated cooling time, larger than the age of the Universe at the cluster redshift. The entropy profile shows a flat core with a central entropy of , remarkably similar to the entropy floor observed in nearby clusters, and a rising profile beyond typically 0.1 virial radius. Implications of our results, in terms of non-gravitational physics in cluster formation, are discussed.