We studied the temperature and metal abundance distributions of the intra-cluster medium (ICM) in a group of galaxies NGC 1550 observed with Suzaku. The NGC 1550 is classified as a fossil group, which have few bright member galaxies except for the ce
ntral galaxy. Thus, such a type of galaxy is important to investigate how the metals are enriched to the ICM. With the Suzaku XIS instruments, we directly measured not only Si, S, and Fe lines but also O and Mg lines and obtained those abundances to an outer region of ~0.5 r_180 for the first time, and confirmed that the metals in the ICM of such a fossil group are indeed extending to a large radius. We found steeper gradients for Mg, Si, S, and Fe abundances, while O showed almost flat abundance distribution. Abundance ratios of alpha-elements to Fe were similar to those of the other groups and poor clusters. We calculated the number ratio of type II to type Ia supernovae for the ICM enrichment to be 2.9 +- 0.5 within 0.1 r_180, and the value was consistent with those for the other groups and poor clusters observed with Suzaku. We also calculated metal mass-to-light ratios (MLRs) for Fe, O and Mg with B-band and K-band luminosities of the member galaxies of NGC 1550. The derived MLRs were comparable to those of NGC 5044 group in the r<0.1 r_180 region, while those of NGC 1550 are slightly higher than those of NGC 5044 in the outer region.
We studied the high temperature plasma in the direction of the Sculptor supercluster at z=0.108 with Suzaku. Suzaku carried out four observations in the supercluster: namely, A2811, A2811 offset, A2804, A2801 regions in 2005 Nov.--Dec., including the
regions beyond the virial radii of these clusters. The study needed precise background estimation because the measured intensity of the redshifted lines, especially those from oxygen, were strongly affected by the the Galactic emission. The spectra taken in the regions outside of the virial radii of the member clusters were used as the background which included both the Galactic and Cosmic X-ray Background (CXB) components. We also used the background data which were taken near the Sculptor supercluster. Temperature and metal abundance profiles were determined to the virial radii of the member clusters, and then we searched for the oxygen line emission in the region outside of the virial radii of the clusters. As a result, the temperature of the clusters decreased toward the virial radii, and the spectral fits for the filament region did not require extra component other than the Galactic and CXB components. We constrained the intensities of O VII and O VIII lines to be less than 8.1 and 5.1 photons cm^-2 s^-1 arcmin^-2, respectively, as 2-sigma upper limits. The intensity of O VII indicates n_H < 1.6e-5 cm^-3 (Z/0.1 Z_solar)^-1/2 (L/25 Mpc)^-1/2, which corresponds to an over density, delta < 60 (Z/0.1 Z_solar)^-1/2 (L/25 Mpc)^-1/2.
Temperature and abundance distributions of the intra-cluster medium (ICM) in the NGC 507 group of galaxies were studied with Suzaku. Observed concentric annular spectra were well-represented by a two temperature model for ICM, and we found steeper ab
undance gradients for Mg, Si, S, and Fe compared with O in the central region. Abundance ratios of alpha-elements to iron were found to be similar to those in other groups and poor clusters. We calculated metal mass-to-light ratios for Fe, O and Mg (IMLR, OMLR, MMLR) for NGC 507, and values for different systems were compared. Hotter and richer systems tend to show higher values of IMLR, OMLR, and MMLR. OMLR and MMLR were measured to an outer region for the first time with Suzaku, while IMLR was consistent with that with ASCA. We also looked into 2-dimensional map of the hardness ratio, but found no significant deviation from the circular symmetry.
We carried out 3 observations of the cluster of galaxies AWM 7, for the central region and 20-east and 20-west offset regions, with Suzaku. Temperature and abundance profiles are measured out to 27~ 570 /h_70 kpc, which corresponded to ~0.35 r_180. T
he temperature of the intra-cluster medium (ICM) slightly decreases from 3.8 keV at the center to 3.4 keV in ~0.35 r_180 region, indicating a flatter profile than those in other nearby clusters. Abundance ratio of Si to Fe is almost constant in our observation, while Mg to Fe ratio increases with radius from the cluster center. O to Fe ratio in the west region shows increase with radius, while that in the east region is almost flat, though the errors are relatively large. These features suggest that the enrichment process is significantly different between products of type II supernovae (O and Mg) and those by type Ia supernovae (Si and Fe). We also examined positional shift of the central energy of He-like Fe-Ka line, in search of possible rotation of the ICM. The 90% upper limit for the line-of-sight velocity difference was derived to be v ~ 2000 km/s, suggesting that the ellipticity of AWM 7 is rather caused by a recent directional infall of the gas along the large-scale filament.
