Metal distributions out to 0.5 r180 in the intracluster medium of four
  galaxy groups observed with Suzaku
  We studied the distributions of metal abundances and metal-mass-to-light
ratios in the intracluster medium (ICM) of four galaxy groups, MKW 4, HCG 62,
the NGC 1550 group, and the NGC 5044 group, out to 0.5 r180 observed with
Suzaku. The Fe abundance decreases with radius, and about 0.2-0.4 solar beyond
0.1 r180. At a given radius in units of r180, the Fe abundance in the ICM of
the four galaxy groups were consistent or smaller than those of clusters of
galaxies. The Mg/Fe and Si/Fe ratios in the ICM are nearly constant at the
solar ratio out to 0.5 r180. We also studied systematic uncertainties in the
derived metal abundances comparing the results from two versions of atomic data
for astrophysicists (ATOMDB) and single- and two temperature model fits. Since
the metals have been synthesized in galaxies, we collected K-band luminosities
of galaxies from Two Micron All Sky Survey catalogue (2MASS) and calculated the
integrated iron-mass-to-light-ratios (IMLR), or the ratios of the iron mass in
the ICM to light from stars in galaxies. The groups with smaller gas mass to
light ratios have smaller IMLR values and the IMLR inversely correlated with
the entropy excess. Based on these abundance features, we discussed the past
history of metal enrichment process in groups of galaxies.
