"An X-ray review of MS 1054-0321: Hot or not?"

XMM-Newton observations are presented for the z=0.83 cluster of galaxies MS 1054-0321, the highest redshift cluster in the Einstein Extended Medium Sensitivity Survey (EMSS). The temperature inferred by the XMM-Newton data, T=7.2+0.7-0.6 keV, is much lower than the temperature previously reported from ASCA data, T=12.3+3.1-2.2 keV (Donahue et al. 1998), and a little lower than the Chandra temperature, T=10.4+1.7-1.5 keV, determined by Jeltema et al. 2001. The discrepancy between the newly derived temperature and the previously derived temperatures is discussed in detail. If one allows the column density to be a free parameter, then the best fit temperature becomes T=8.6+1.2-1.1 keV, and the best fit column density becomes NH=1.33+0.15-0.14 ×1020 atoms cm-2. The iron line is well detected in the XMM-Newton spectrum with a value for the abundance of Z=0.33+0.19-0.18 Z⊙, in very good agreement with previous determinations. The derived XMM X-ray luminosity for the overall cluster in the 2-10 keV energy band is LX= (3.81±0.19) ×1044 h-2 erg s-1 while the bolometric luminosity is LBOL=(8.05±0.40) ×1044 h-2 erg s-1. The XMM-Newton data confirm the substructure in the cluster X-ray morphology already seen by ROSAT and in much more detail by Chandra. We find that only two of the three clumps detected in the weak lensing mass reconstruction image are visible in X-rays, as already noted by \cite{jel01}. The central weak lensing clump is coincident with the main cluster component and has a temperature T=8.1+1.3-1.2 keV. The western weak lensing clump coincides with the western X-ray component which is much cooler with a temperature T=5.6+0.8-0.6 keV. The optically measured velocity dispersion, obtained from 145 cluster redshifts, is consistent with the velocity dispersion expected from the σV-TX relationship once the XMM-Newton temperature is used. MS 1054-0321 fits well in the σ ∝ T1/2 correlation available in the literature and derived from information collected for all clusters at redshfits of z≤1.27 known today and with a measured X-ray temperature. The cluster temperature seems to be commensurate with the predictions from its X-ray luminosity from the LX-TX relation of local clusters. Given the newly determined temperature, MS 1054-0321 is no longer amongst the hottest clusters known. Data presented here used the XMM-Newton facility.