Resolving galaxy cluster gas properties at z~1 with XMM-Newton and
  Chandra
  We present a pilot X-ray study of the five most massive ($M_{500}>5 \times
10^{14} M_{\odot}$), distant (z~1), galaxy clusters detected via the
Sunyaev-Zeldovich effect. We optimally combine XMM-Newton and Chandra X-ray
observations by leveraging the throughput of XMM to obtain spatially-resolved
spectroscopy, and the spatial resolution of Chandra to probe the bright inner
parts and to detect embedded point sources. Capitalising on the excellent
agreement in flux-related measurements, we present a new method to derive the
density profiles, constrained in the centre by Chandra and in the outskirts by
XMM. We show that the Chandra-XMM combination is fundamental for morphological
analysis at these redshifts, the Chandra resolution being required to remove
point source contamination, and the XMM sensitivity allowing higher
significance detection of faint substructures. The sample is dominated by
dynamically disturbed objects. We use the combined Chandra-XMM density profiles
and spatially-resolved temperature profiles to investigate thermodynamic
quantities including entropy and pressure. From comparison of the scaled
profiles with the local REXCESS sample, we find no significant departure from
standard self-similar evolution, within the dispersion, at any radius, except
for the entropy beyond 0.7$R_{500}$. The baryon mass fraction tends towards the
cosmic value, with a weaker dependence on mass than observed in the local
Universe. We compare with predictions from numerical simulations. The present
pilot study demonstrates the utility and feasibility of spatially-resolved
analysis of individual objects at high-redshift through the combination of XMM
and Chandra observations. Observations of a larger sample will allow a fuller
statistical analysis to be undertaken, in particular of the intrinsic scatter
in the structural and scaling properties of the cluster population. (abridged)
