Impact of Chandra calibration uncertainties on galaxy cluster
  temperatures: application to the Hubble Constant
  We perform a uniform, systematic analysis of a sample of 38 X-ray galaxy
clusters with three different Chandra calibrations. The temperatures change
systematically between calibrations. Cluster temperatures change on average by
roughly ~6% for the smallest changes and roughly ~13% for the more extreme
changes between calibrations. We explore the effects of the changing cluster
spectral properties on Sunyaev-Zel'dovich effect (SZE) and X-ray determinations
of the Hubble constant. The Hubble parameter changes by +10% and -13% between
the current calibration and two previous Chandra calibrations, indicating that
changes in the cluster temperature basically explain the entire change in H_0.
Although this work focuses on the difference in spectral properties and
resultant Hubble parameters between the calibrations, it is intriguing to note
that the newer calibrations favor a lower value of the Hubble constant, H_0 ~
60 km s-1 Mpc-1, typical of results from SZE/X-ray distances. Both galaxy
clusters themselves and the details of the instruments must be known precisely
to enable reliable precision cosmology with clusters, which will be feasible
with combined efforts from ongoing observations and planned missions and
observatories covering a wide range of wavelengths.
