Suzaku Observation of Abell 1555 and Abell 1558: Searching for
  Non-thermal Emission from Large Scale Structure Formation
  We report X-ray observations of two galaxy clusters Abell 1555 and Abell 1558
with Suzaku, which are included in a large scale filamentary structure and a
supercluster, to search for non-thermal emission driven by shocks produced in
structure formation. These two clusters are detected by Suzaku/XIS for the
first time in the X-ray band of 0.5-7 keV. No significant flux is detected by
HXD in the energy band of 13-40 keV, and upper limits are reported. From the
analysis of the XIS data, we find that the spectrum of A1555 is fit by a
thermal plus power-law model, significantly better than a single-temperature
pure thermal spectrum. If this power-law component is due to inverse-Compton
scattering, the fraction of total baryon energy imparted to non-thermal
electrons is consistent with the typical value inferred from the observation of
other clusters. However, other scenarios (e.g., under lying AGNs,
multi-temperature thermal models) cannot be excluded and further investigation
of this system is desired. Basic physical properties of A1555 (e.g., total
mass) are also reported.
