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X-Ray Study of the Outer Region of Abell 2142 with Suzaku

Authors :
Akamatsu, H.
Hoshino, A.
Ishisaki, Y.
Ohashi, T.
Sato, K.
Takei, Y.
Ota, N.
Publication Year :
2011

Abstract

We observed outer regions of a bright cluster of galaxies A2142 with Suzaku. Temperature and brightness structures were measured out to the virial radius ($r_{200}$) with good sensitivity. We confirmed the temperature drop from 9 keV around the cluster center to about 3.5 keV at $r_{200}$, with the density profile well approximated by the $\beta$ model with $\beta = 0.85$. Within $0.4\r_{200}$, the entropy profile agrees with $r^{1.1}$, as predicted by the accretion shock model. The entropy slope becomes flatter in the outer region and negative around $r_{200}$. These features suggest that the intracluster medium in the outer region is out of thermal equilibrium. Since the relaxation timescale of electron-ion Coulomb collision is expected to be longer than the elapsed time after shock heating at $r_{200}$, one plausible reason of the low entropy is the low electron temperature compared to that of ions. Other possible explanations would be gas clumpiness, turbulence and bulk motions of ICM\@. We also searched for a warm-hot intergalactic medium around $r_{200}$ and set an upper limit on the oxygen line intensity. Assuming a line-of-sight depth of 2 Mpc and oxygen abundance of 0.1 solar, the upper limit of an overdensity is calculated to be 280 or 380, depending on the foreground assumption.<br />Comment: 14 pages, 8 figures

Details

Database :
arXiv
Publication Type :
Report
Accession number :
edsarx.1106.5653
Document Type :
Working Paper
Full Text :
https://doi.org/10.1093/pasj/63.sp3.S1019