Gas bulk motion in the Perseus cluster measured with SUZAKU
  We present the results from Suzaku observations of the Perseus galaxy
cluster, which is relatively close, the brightest in the X-ray sky and a
relaxed object with a cool core. A number of exposures of central regions and
offset pointing with the X-ray Imaging Spectrometer cover a region within radii
of 20'-30'. The central data are used to evaluate the instrumental energy-scale
calibration with accuracy confirmed to within around 300 km/s, by the spatial
and temporal variation of the instruments. These deep and well-calibrated data
are used to measure X-ray redshifts of the intracluster medium. A hint of gas
bulk motion, with radial velocity of about -(150-300) km/s, relative to the
main system was found at 2-4 arcmin (45-90kpc) west of the cluster center,
where an X-ray excess and a cold front were found previously. No other velocity
structure was discovered. Over spatial scales of 50-100kpc and within 200kpc
radii of the center, the gas-radial-velocity variation is below 300 km/s, while
over scales of 400 kpc within 600 kpc radii, the variation is below 600 km/s.
These X-ray redshift distributions are compared spatially with those of optical
member galaxies for the first time in galaxy clusters. Based on X-ray line
widths gas turbulent velocities within these regions are also constrained
within 1000-3000 km/s. These results of gas dynamics in the core and larger
scales in association with cluster merger activities are discussed and future
potential of high-energy resolution spectroscopy with ASTRO-H is considered.
