Chandra X-ray observations of Abell 1835 to the virial radius
  We report the first Chandra detection of emission out to the virial radius in
the cluster Abell 1835 at z=0.253. Our analysis of the soft X-ray surface
brightness shows that emission is present out to a radial distance of 10 arcmin
or 2.4 Mpc, and the temperature profile has a factor of ten drop from the peak
temperature of 10 keV to the value at the virial radius. We model the Chandra
data from the core to the virial radius and show that the steep temperature
profile is not compatible with hydrostatic equilibrium of the hot gas, and that
the gas is convectively unstable at the outskirts. A possible interpretation of
the Chandra data is the presence of a second phase of warm-hot gas near the
cluster's virial radius that is not in hydrostatic equilibrium with the
cluster's potential. The observations are also consistent with an alternative
scenario in which the gas is significantly clumped at large radii.
