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Issue A&A
Volume 420, Number 3, June IV 2004
Page(s) 853 - 872
Section Cosmology (including clusters of galaxies)
DOI http://dx.doi.org/10.1051/0004-6361:20035687



A&A 420, 853-872 (2004)
DOI: 10.1051/0004-6361:20035687

The XMM-NEWTON $\Omega$ project

I. The X-ray luminosity-temperature relation at $\mathsf{\textit{z}>0.4}$
D. H. Lumb1, J. G. Bartlett2, 3, A. K. Romer4, 5, A. Blanchard6, D. J. Burke7, C. A. Collins8, R. C. Nichol4, M. Giard9, P. B. Marty6, J. Nevalainen7, R. Sadat6 and S. C. Vauclair6

1  Science Payloads and Advanced Concepts Office, European Space Agency, ESTEC, 2200AG Noordwijk, The Netherlands
2  APC - Université Paris 7/PCC - Collège de France, 11 Pl. Marcelin Berthelot, 75231 Paris Cedex 05, France
3  Centre de Données astronomiques de Strasbourg, 11 rue de l'Université, 67000 Strasbourg, France
4  Physics Department, Carnegie Mellon University, Pittsburgh, PA 15213, USA
5  Astronomy Centre, Dept. of Physics and Astronomy, University of Sussex, Brighton, UK
6  Laboratoire d'Astrophysique, OMP, CNRS, UPS, 14 Av. Ed. Belin, 31400 Toulouse, France
7  Harvard-Smithsonian Center for Astrophysics, 60 Garden Street, Cambridge, MA 02138, USA
8  Astrophysics Research Institute, Liverpool John Moores University, Twelve Quays House, Egerton Wharf, Birkenhead CH41 1LD, UK
9  Centre d'Étude Spatiale des Rayonnements, 9 avenue du Colonel Roche, BP 4346, 31028 Toulouse, France

(Received 14 November 2003 / Accepted 17 March 2004 )

Abstract
We describe XMM-Newton Guaranteed Time observations of a sample of eight high redshift (0.45<z<0.62) clusters. The goal of these observations was to measure the luminosity and the temperature of the clusters to a precision of ~10%, leading to constraints on the possible evolution of the luminosity-temperature ( Lx-Tx) relation, and ultimately on the values of the matter density, $\Omega_{\rm M}$, and, to a lesser extent, the cosmological constant $\Omega_{\Lambda}$. The clusters were drawn from the SHARC and 160 Square Degree (160SD) ROSAT surveys and span a bolometric (0.0-20 keV) luminosity range of 2.0 to $14.4 \times 10^{44}$ erg s -1 ( H0=50, $\Omega_{\rm M}=1$, $\Omega_{\Lambda}=0$). Here we describe our data analysis techniques and present, for the first time with XMM-Newton, a Lx-Tx relation. For each of the eight clusters in the sample, we have measured total ( $r<r_{\rm virial}$) bolometric luminosities, performed $\beta$-model fits to the radial surface profiles and made spectral fits to a single temperature isothermal model. We describe data analysis techniques that pay particular attention to background mitigation. We have also estimated temperatures and luminosities for two known clusters (Abell 2246 and RX J1325.0-3814), and one new high redshift cluster candidate (XMMU J084701.8+345117), that were detected off-axis. Characterizing the Lx-Tx relation as $L_{x} = L_{6} (\frac{T}{6~\rm keV})^{\alpha}$, we find $L_{6}=15.9 ^{+7.6}_{-5.2} \times 10^{44}$  erg s -1  and $\alpha=2.7\pm0.4$ for an $\Omega_{\Lambda}=0.0, \Omega_{\rm M}=1.0$, H0=50 km s -1 Mpc -1 cosmology at a typical redshift $z \sim 0.55$. Comparing with the low redshift study by Markevitch (1998), we find $\alpha$ to be in agreement, and assuming Lx-Tx to evolve as (1+z)A , we find $A=0.68\pm0.26$ for the same cosmology and A=1.52+0.26-0.27 for an $\Omega_{\Lambda}=0.7, \Omega_{\rm M}=0.3$ cosmology. Our A values are very similar to those found previously by Vikhlinin et al. (2002) using a compilation of Chandra observations of 0.39<z<1.26 clusters. We conclude that there is now evidence from both XMM-Newton and Chandra for an evolutionary trend in the Lx-Tx relation. This evolution is significantly below the level expected from the predictions of the self-similar model for an $\Omega_{\Lambda}=0.0, \Omega_{\rm M}=1.0$, cosmology, but consistent with self-similar model in an $\Omega_{\Lambda}=0.7, \Omega_{\rm M}=0.3$ cosmology. Our observations lend support to the robustness and completeness of the SHARC and 160SD surveys.


Key words: X-rays: galaxies: clusters

Offprint request: D. H. Lumb, dlumb@rssd.esa.int

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© ESO 2004


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