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Title:
Intracluster Medium Entropy Profiles for a Chandra Archival Sample of Galaxy Clusters
Authors:
Cavagnolo, Kenneth W.; Donahue, Megan; Voit, G. Mark; Sun, Ming
Affiliation:
AA(Department of Physics and Astronomy, Michigan State University, East Lansing, MI 48824-2320, USA ; Department of Physics and Astronomy, University of Waterloo, Waterloo, ON N2L 2G1, Canada ; ), AB(Department of Physics and Astronomy, Michigan State University, East Lansing, MI 48824-2320, USA ), AC(Department of Physics and Astronomy, Michigan State University, East Lansing, MI 48824-2320, USA ), AD(Department of Physics and Astronomy, Michigan State University, East Lansing, MI 48824-2320, USA ; Department of Astronomy, University of Virginia, Charlottesville, VA 22904, USA)
Publication:
The Astrophysical Journal Supplement, Volume 182, Issue 1, pp. 12-32 (2009). (ApJS Homepage)
Publication Date:
05/2009
Origin:
IOP
ApJ Keywords:
astronomical data bases: miscellaneous, cooling flows, X-rays: galaxies: clusters, X-rays: general
DOI:
10.1088/0067-0049/182/1/12
Bibliographic Code:
2009ApJS..182...12C

Abstract

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 fitted by a model which is a power law at large radii and approaches a constant value at small radii: K(r) = K 0 + K 100(r/100 kpc)α, where K 0 quantifies the typical excess of core entropy above the best-fitting power law found at larger radii. We also show that the K 0 distributions of both the full archival sample and the primary Highest X-Ray Flux Galaxy Cluster Sample of Reiprich (2001) are bimodal with a distinct gap between K 0 ≈ 30-50 keV cm2 and population peaks at K 0 ~ 15 keV cm2 and K 0 ~ 150 keV cm2. The effects of point-spread function smearing and angular resolution on best-fit K 0 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 K 0 is also considered, and we find no indication that K 0 is significantly impacted by either. For completeness, we include previously unpublished optical spectroscopy of Hα 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.

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