Astronomy and Astrophysics – Astrophysics – Cosmology and Extragalactic Astrophysics
Scientific paper
2009-02-11
Astronomy and Astrophysics
Astrophysics
Cosmology and Extragalactic Astrophysics
Accepted to ApJ Supplement, 46 pages, 8 figures (2 color), 5 tables,
Scientific paper
10.1088/0067-0049/182/1/12
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 For completeness, we include previously unpublished optical spectroscopy of Halpha and [N II] emission lines discussed in Cavagnolo et al.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.
Cavagnolo Kenneth W.
Donahue Megan
Sun Ming
Voit Gerard Mark
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