An X-ray Spectroscopic Search for Dark Matter in the Perseus Cluster
  with Suzaku
  We present the results from deep Suzaku observations of the central region of
the Perseus cluster. Bulbul et al. (2014) reported the detection by XMM-Newton
instruments of an unidentified X-ray emission line at an energy around 3.5keV
in spectra for the Perseus and other clusters. They argued for a possibility of
the decay of sterile neutrino, a dark matter candidate. We examine Suzaku X-ray
Imaging Spectrometer (XIS) spectra of the Perseus cluster for evidence in the
3.5keV line and other possible dark matter features in the 2-6keV energy band.
In order to search for and constrain a weak line feature with the XIS,
observations of the Crab nebula are used to evaluate the system's effective
area. We found no line feature at the claimed position with a systematic line
flux upper limit at a half (1.5eV in line equivalent width) of the claimed
best-fit value by Bulbul et al. We discuss this inconsistency in terms of
instrumental calibration errors and modeling of continuum emission. Future
prospects for high-energy resolution spectroscopy with ASTRO-H are presented.
