749 research outputs found
Distribution of Si, Fe, and Ni in the Intracluster Medium of the Coma Cluster
We studied the distributions of Si, Fe, and Ni in the intracluster medium
(ICM) of the Coma cluster, one of the largest clusters in the nearby universe,
using XMM-Newton data up to 0.5 r180 and Suzaku data of the central region up
to 0.16 r180. Using the flux ratios of Ly alpha of H-like Si and 7.8 keV blend
to K alpha of He-like Fe, the abundance ratios of Si to Fe and Ni to Fe of the
ICM were derived using APEC model v2.0.1. The Si/Fe ratio in the ICM of the
Coma cluster shows no radial gradient. The emission weighted averages of the
Si/Fe ratio in the ICM within 0.0--0.2 r180, 0.2--0.5 r180, and 0.0--0.5 r180
are 0.97 +- 0.11, 1.05 +- 0.36 and 0.99 +- 0.13, respectively, in solar units
using the solar abundance of Lodders (2003). These values are close to those of
smaller clusters and groups of galaxies. Using the Suzaku data of the central
region, the derived Ni/Fe ratio of the ICM is 0.6--1.5 in solar units,
according to the same solar abundance table. The systematic difference in the
derived abundance ratios by different plasma codes are about 10%. Therefore,
for the ICM in the Coma cluster, the abundance pattern of Si, Fe, and Ni is
consistent with the same mixture of the yields of SN II and SN Ia in our
Galaxy. Within 0.5 r180}, the cumulative iron-mass-to-light ratio increases
with radius, and its radial profile is similar to those of relaxed smaller
clusters with cD galaxies at their center. Considering the observed Si/Fe
ratio, the cumulative metal-mass-to-light ratios at 0.5 r180 are compared with
theoretical expectations.Comment: 10 pages, 7 figures, accepted for publication in PAS
Temperature and Metallicity in the Intra-cluster Medium of ABELL 262 observed with Suzaku
We studied the temperature and abundance distributions of intra-cluster
medium (ICM) in the Abell 262 cluster of galaxies observed with Suzaku. Abell
262 is a bright, nearby poor cluster with ICM temperature of ~2 keV, thus
providing useful information about the connection of ICM properties between
groups and clusters of galaxies. The observed spectrum of the central region
was well-represented by two temperature models, and the spectra for the outer
regions were described by single temperature model. With the XIS instrument, 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 ~0.43 r_180 for the first time.
We found steep gradients for Mg, Si, S, and Fe abundances, while O showed
almost flat abundance distribution. Abundance ratios of alpha-elements to Fe
were found to be similar to those of the other clusters and groups. We
calculated the number ratio of type II to type Ia supernovae for the ICM
enrichment to be 3.0 +- 0.6 within 0.1 r_180, and the value was consistent with
those for other clusters and groups. We also calculated metal mass-to-light
ratios (MLRs) for Fe, O and Mg (IMLR, OMLR, MMLR) with B-band and K-band
luminosities of the member galaxies of Abell 262. The derived MLRs were
comparable to those for other clusters with kT = 3-4 keV.Comment: 12 pages, 8 figures, accepted for publication in PAS
Suzaku observations of subhalos in the Coma cluster
We observed three massive subhalos in the Coma cluster with {\it Suzaku}.
These subhalos, labeled "ID 1", "ID 2", and "ID 32", were detected with a
weak-lensing survey using the Subaru/Suprime-Cam (Okabe et al. 2014a), and are
located at the projected distances of 1.4 , 1.2 , and 1.6
from the center of the Coma cluster, respectively. The subhalo "ID 1"
has a compact X-ray excess emission close to the center of the weak-lensing
mass contour, and the gas mass to weak-lensing mass ratio is about 0.001. The
temperature of the emission is about 3 keV, which is slightly lower than that
of the surrounding intracluster medium (ICM) and that expected for the
temperature vs. mass relation of clusters of galaxies. The subhalo "ID 32"
shows an excess emission whose peak is shifted toward the opposite direction
from the center of the Coma cluster. The gas mass to weak-lensing mass ratio is
also about 0.001, which is significantly smaller than regular galaxy groups.
The temperature of the excess is about 0.5 keV and significantly lower than
that of the surrounding ICM and far from the temperature vs. mass relation of
clusters. However, there is no significant excess X-ray emission in the "ID 2"
subhalo. Assuming an infall velocity of about 2000 , at the
border of the excess X-ray emission, the ram pressures for "ID 1" and "ID 32"
are comparable to the gravitational restoring force per area. We also studied
the effect of the Kelvin-Helmholtz instability to strip the gas. Although we
found X-ray clumps associated with the weak-lensing subhalos, their X-ray
luminosities are much lower than the total ICM luminosity in the cluster
outskirts.Comment: 19 pages, 8 figures, ApJ in pres
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