Effects of SNe II and SNe Ia Feedback on the Chemo-Dynamical Evolution of Elliptical Galaxies

Abstract

We numerically investigate the dynamical and chemical processes of the formation of elliptical galaxies in a cold dark matter (CDM) universe, in order to understand the origin of the mass-dependence of the photometric properties of elliptical galaxies. Our three-dimensional TREE N-body/SPH numerical simulations of elliptical galaxy formation take into account both Type II (SNe II) and Type Ia (SNe Ia) supernovae (SNe) and follow the time evolution of the abundances of several chemical elements (C, O, Ne, Mg, Si, and Fe). Moreover we compare different strengths of SNe feedback.In combination with stellar population synthesis, we derive the photometric properties of simulation end-products, including the magnitude, color, half-light radius, and abundance ratios, and compare them with the observed scaling relations directly and quantitatively. We find that the extremely strong influence of SNe is required to reproduce the observed color-magnitude relation (CMR), where we assume each SN yields energy of 4x10^51 ergs and that 90% of this energy is ejected as kinetic feedback. The feedback affects the evolution of lower mass systems more strongly and induces the galactic wind by which a larger fraction of gas is blown out in a lower mass system. Finally higher mass systems become more metal rich and have redder colors than lower mass systems. We emphasize based on our simulation results that the galactic wind is triggered mainly by SNe Ia rather than SNe II. In addition we examined the Kormendy relation, which prescribes the size of elliptical galaxies, and the [Mg/Fe]--magnitude relation, which provides a strong constraint on the star formation history.