Abundance Patterns in the Interstellar Medium of Early-type Galaxies
  Observed with Suzaku
  We have analyzed 17 early-type galaxies, 13 ellipticals and 4 S0's, observed
with Suzaku, and investigated metal abundances (O, Mg, Si, and Fe) and
abundance ratios (O/Fe, Mg/Fe, and Si/Fe) in the interstellar medium (ISM). The
emission from each on-source region, which is 4 times effective radius, r_e, is
reproduced with one- or two- temperature thermal plasma models as well as a
multi-temperature model, using APEC plasma code v2.0.1. The multi-temperature
model gave almost the same abundances and abundance ratios with the 1T or 2T
models. The weighted averages of the O, Mg, Si, and Fe abundances of all the
sample galaxies derived from the multi-temperature model fits are 0.83+-0.04,
0.93+-0.03, 0.80+-0.02, and 0.80+-0.02 solar, respectively, in solar units
according to the solar abundance table by Lodders (2003). These abundances show
no significant dependence on the morphology and environment. The systematic
differences in the derived metal abundances between the version 2.0.1 and 1.3.1
of APEC plasma codes were investigated. The derived O and Mg abundances in the
ISM agree with the stellar metallicity within a aperture with a radius of one
r_e derived from optical spectroscopy. From these results, we discuss the past
and present SN Ia rates and star formation histories in early-type galaxies.
