Abundance patterns in the Interstellar Medium of early-type galaxies observed with Suzaku

We investigated the metal abundances/abundance ratios of the hot interstellar medium (ISM), in 17 early-type galaxies with Suzaku (Konami et al. 2014). The derived O and Mg abundances in the ISM within 4 times effective radius, which include most of stars, agree with the stellar metallicity within a one effective radius derived from optical spectroscopy. Because the O and Mg in the ISM have been provided by stellar massloos, the results are very reasonable and indicates relatively small systematic errors in the measurements with these optical and X-ray observations. The abundance ratios of O/Fe, Mg/Fe and Si/Fe in the ISM of almost galaxies are close to the solar ratio. Since the abundances/abundance ratios show no significant dependence on the morphology and environment, the major star formation history should be similar among these objects. Furthermore, the Fe in the ISM have been provided by stellar massloos and present SN Ia. The Fe abundance in the ISM is significantly smaller than the expected value derived from optical observations, indicates a low present SN Ia rate. From these results, we discuss the past and present SN Ia rates and star formation histories in early-type galaxies.