A shock near the virial radius of the Perseus Cluster
  Previous X-ray studies of the Perseus Cluster, consisting of 85 Suzaku
pointings along eight azimuthal directions, revealed a particularly steep
decrease in the projected temperature profile near the virial radius (~r200)
towards the northwest (NW). To further explore this shock candidate, another 4
Suzaku observations on the NW edge of the Perseus Cluster have been obtained.
These deeper data were designed to provide the best possible control of
systematic uncertainties in the spectral analysis. Using the combined Suzaku
observations, we have carefully investigated this interesting region by
analyzing the spectra of various annuli and extracting projected thermodynamic
profiles. We find that the projected temperature profile shows a break near
r200, indicating a shock with M = 1.9+-0.3. Corresponding discontinuities are
also found in the projected emission measure and the density profiles at the
same location. This evidence of a shock front so far away from the cluster
center is unprecedented, and may provide a first insight into the properties of
large-scale virial shocks which shape the process of galaxy cluster growth.
