Azimuthally Resolved X-Ray Spectroscopy to the Edge of the Perseus
  Cluster
  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 degrees = 2.6 Mpc, to and
beyond the virial radius r_200 ~ 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>0.4r_200 is relatively
flat, with a best-fit power-law index of 1.69+/-0.13 significantly smaller than
expected from numerical simulations. The entropy 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 gravitational
collapse. The pressure profile beyond ~0.6r_200 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 flattening of the entropy profiles outside
~0.6r_200, 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.
