E. Churazov, A. Vikhlinin, I. Zhuravleva, A. Schekochihin, I. Parrish, R. Sunyaev, W. Forman, H. Boehringer, S. Randall
X-ray surface brightness fluctuations in the core ($650 \times 650$ kpc)
region of the Coma cluster observed with XMM-Newton and Chandra are analyzed
using a 2D power spectrum approach. The resulting 2D spectra are converted to
3D power spectra of gas density fluctuations. The characteristic amplitude of
the volume filling density fluctuations relative to the smooth underlying
density distribution varies from 7-10% on scales of $\sim$500 kpc down to
$\sim$5% at scales $\sim$ 30 kpc. On smaller spatial scales, projection effects
smear the density fluctuations by a large factor, precluding strong limits on
the fluctuations in 3D. On the largest scales probed (hundreds of kpc), the
dominant contributions to the observed fluctuations most likely arise from
perturbations of the gravitational potential by the two most massive galaxies
in Coma, NGC4874 and NGC4889, and the low entropy gas brought to the cluster by
an infalling group. Other plausible sources of density fluctuations are
discussed, including turbulence, metal abundance variations, and unresolved
sources.
View original:
http://arxiv.org/abs/1110.5875
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