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 \sim 10 % , leading to constraints on the possible evolution of the luminosity–temperature ( L _ { x } - T _ { x } ) relation , and ultimately on the values of the matter density , \Omega _ { 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 } ( H _ { o } =50 , \Omega _ { M } =1 , \Omega _ { \Lambda } =0 ) .
Here we describe our data analysis techniques and present , for the first time with XMM-Newton , a L _ { x } - T _ { x } relation .
For each of the eight clusters in the sample , we have measured total ( r < r _ { 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 RXJ1325.0-3814 ) , and one new high redshift cluster candidate ( XMMU J084701.8+345117 ) , that were detected off-axis .
Characterizing the L _ { x } - T _ { x } relation as L _ { x } = L _ { 6 } ( \frac { T } { 6 keV } ) ^ { \alpha } , we find L _ { 6 } = 15.9 ^ { +7.6 } _ { -5.2 } \times 10 ^ { 44 } erg s ^ { -1 } and \alpha =2.7 \pm 0.4 for an \Omega _ { \Lambda } = 0.0 , \Omega _ { M } = 1.0 , H _ { 0 } = 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 L _ { x } - T _ { x } to evolve as ( 1 + z ) ^ { A } , we find A =0.68 \pm 0.26 for the same cosmology and A = 1.52 ^ { +0.26 } _ { -0.27 } for an \Omega _ { \Lambda } = 0.7 , \Omega _ { 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 L _ { x } - T _ { x } relation .
This evolution is significantly below the level expected from the predictions of the self-similar model for an \Omega _ { \Lambda } = 0.0 , \Omega _ { M } = 1.0 , cosmology , but consistent with self-similar model in an \Omega _ { \Lambda } = 0.7 , \Omega _ { M } = 0.3 cosmology .
Our observations lend support to the robustness and completeness of the SHARC and 160SD surveys .