Chemo-dynamical evolution of colliding dwarf spheroidal galaxies

We present the first result from our project of chemo-dynamical simulations of dwarf spheroidal galaxies (dSphs). The chemical evolution of dSphs is affected by physical processes such as star formation and explosive nucleosynthesis as well as the dynamical merging histories among dSphs. It is thus important, first, to include nucleosynthetic information, and second, to carry out numerical simulations to clarify the chemo-dynamical evolution of dSphs. Therefore, we have implemented gas cooling, star formation rate, and chemical evolution to the N-body/smoothed particle hydrodynamic (SPH) code, Gadget-2 for the computation of chemo-dynamical evolution of dSphs. In particular, we study the collision effects of dSphs on the chemo-dynamical evolution. We derived star formation rate and metallicity distribution of an isolated model and a collided model. In the collided model, the two same mass dSphs are collided and merged. Both the isolated and collided models show the starburst at ∼ 0.3 Gyr after the start of the simulation. The star formation rate of the isolated model is continuous and quenched. In contrast, the starburst can be clearly seen at the time of the encounter of two dSphs in the collided model. The effects of collision can also be seen in the metallicity distribution. The peak of the metallicity distribution of the isolated model is at [Fe/H] ∼ −2.5, though the peak of the collided model is at [Fe/H] ∼ −1.6. The result implies that the collision of dSphs strongly affects the chemo-dynamical evolution of dSphs.