Elemental Abundance Ratios and Origin of Very High (Fe/O) in Extremely Metal-Poor Galaxies

speaker: Kuria Watanabe

Extreme metal-poor galaxies (EMPGs) are low metallicity, and young.
Elemental abundance ratios of EMPGs provide insight into star formation in the early stages of galaxy formation. Although the metallicity of EMPGs is less than 10 % of solar, several EMPGs with [Fe/O] as large as the solar abundance are reported.
Since EMPG is a young galaxy, type Ia supernovae have probably not yet occurred.
Therefore, we investigate the possibility that pair-instability supernovae (PISN) and hypernovae (HN) with high explosion energy produced rich iron. Using our initial mass function and the yields of previous studies, we develop the models of the chemical evolution of galaxies and compare them to observations. We focus on S and Ar, which are abundant in PISN. Since the [S/O] and [Ar/O] in EMPG are smaller than in the PISN model, we suggest that the origin of Fe in EMPG is not PISN.
We also study the effects of the supernova explosion energy and the mixing & fallback model (Umeda & Nomoto 2002). We calculate the yields of CCSN and HN using the yield calculation code for the core-collapse supernova (CCSN) model. Using the yield with varying effects of the mixing & fallback model, we develop a model of the chemical evolution of galaxies and introduce the results compared to observations.