Chemodynamical Simulations of Galaxies and the Universe

Abstract

We simulate the formation and evolution of galaxies with a hydrodynamical model including star fromation, supernova feedback, and chemical enrichment. From the comparison with observed elemental abundances, we study the evolution of galaxies and the origin of heavy elements (Galactic Archaeology). A large fraction of hypernovae is required from the observed abundance ratios in the Milky Way Galaxy (namely, [Zn/Fe] ∼ 0). Our progenitor model of SNe Ia based on the single degenerate scenario with the metallicity effect is prefered from the evolution of the abundance ratios (namely, [(α ,Mn,Zn)/Fe]-[Fe/H] relations). In our simulated Milky Way-type galaxy, the kinematical and chemical properties of bulge, disk, and halo are broadly consistent with observations. 80% of the bulge stars are as old as 10 Gyr, and have high [α/Fe], while the disk stars tend to be young and show the decreasing trend of [α/Fe] against [Fe/H]. 80% of thick disk stars are older than ∼ 8 Gyr, and tend to have larger [α/Fe] than in the thin disk. We also predict the frequency distribution in the [X/Fe]-[Fe/H] diagrams from carbon to zinc, depending on the location within the galaxy. In our cosmological simulation, the hypernova feedback play an essential role in suppressing star formation, which results in the cosmic star formation rate history peaked at z ∼ 3 as observed. The hypernova feedback also drives galactic outflows efficiently in low mass galaxies, and these winds eject heavy elements into the intergalactic medium. The ejected baryon and metal fraction is larger for less massive galaxies, which results in the observed mass-metallicity relation of galaxies. We also predict the cosmic supernova and gamma-ray burst rate hisotries, assuming that their progenitors are massive and low-metal hypernovae.