Azimuthally resolved X-ray spectroscopy to the edge of the Perseus Cluster

Urban, O. and Simionescu, A. and Werner, Norbert and Allen, S. W. and Ehlert, S. and Zhuravleva, I. and Morris, R. G. and Fabian, A. C. and Mantz, A. and Nulsen, P. E. J. and Sanders, J. S. and Takei, Y. (2014) Azimuthally resolved X-ray spectroscopy to the edge of the Perseus Cluster. MONTHLY NOTICES OF THE ROYAL ASTRONOMICAL SOCIETY, 437 (4). pp. 3939-3961. ISSN 0035-8711

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Abstract

We present the results from extensive, new observations of the Perseus Cluster of galaxies, obtained as a Suzaku Key Project. The 85 pointings analyzed span eight azimuthal directions out to 2◦ = 2.6 Mpc, to and beyond the virial radius r200 ∼ 1.8 Mpc, offering the most detailed X-ray observation of the intracluster medium (ICM) at large radii in any cluster to date. The azimuthally averaged density profile for r > 0.4r200 is relatively flat, with a best-fit power-law index δ = 1.69 ± 0.13 significantly smaller than expected from numerical simulations. The en- tropy profile in the outskirts lies systematically below the power-law behavior expected from large-scale structure formation models which include only the heating associated with gravi- tational collapse. The pressure profile beyond ∼ 0.6r200 shows an excess with respect to the best-fit model describing the SZ measurements for a sample of clusters observed with Planck. The inconsistency between the expected and measured density, entropy, and pressure profiles can be explained primarily by an overestimation of the density due to inhomogeneous gas distribution in the outskirts; there is no evidence for a bias in the temperature measurements within the virial radius. We find significant differences in thermodynamic properties of the ICM at large radii along the different arms. Along the cluster minor axis, we find a flatten- ing of the entropy profiles outside ∼ 0.6r200, while along the major axis, the entropy rises all the way to the outskirts. Correspondingly, the inferred gas clumping factor is typically larger along the minor than along the major axis.

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