Intracluster Medium Entropy Profiles for a Chandra Archival Sample of
  Galaxy Clusters
  We present radial entropy profiles of the intracluster medium (ICM) for a
collection of 239 clusters taken from the Chandra X-ray Observatory's Data
Archive. Entropy is of great interest because it controls ICM global properties
and records the thermal history of a cluster. Entropy is therefore a useful
quantity for studying the effects of feedback on the cluster environment and
investigating any breakdown of cluster self-similarity. We find that most ICM
entropy profiles are well-fit by a model which is a power-law at large radii
and approaches a constant value at small radii: K(r) = K0 + K100(r/100 kpc),
where K0 quantifies the typical excess of core entropy above the best fitting
power-law found at larger radii. We also show that the K0 distributions of both
the full archival sample and the primary HIFLUGCS sample of Reiprich (2001) are
bimodal with a distinct gap between K0 ~ 30 - 50 keV cm^2 and population peaks
at K0 ~ 15 keV cm^2 and K0 ~ 150 keV cm^2. The effects of PSF smearing and
angular resolution on best-fit K0 values are investigated using mock Chandra
observations and degraded entropy profiles, respectively. We find that neither
of these effects is sufficient to explain the entropy-profile flattening we
measure at small radii. The influence of profile curvature and number of radial
bins on best-fit K0 is also considered, and we find no indication K0 is
significantly impacted by either. For completeness, we include previously
unpublished optical spectroscopy of Halpha and [N II] emission lines discussed
in Cavagnolo et al. (2008a). All data and results associated with this work are
publicly available via the project web site.
