Chemodynamical simulations and galactic archaeology

(Kobayashi)

Chemical Enrichment - Different elements are produced from different types of supernovae with different timescales, with the consequence that elemental abundance ratios evolve inside a galaxy. Using chemical evolution models, the time evolution of elements have been well reproduced in the solar neighbourhood (Fig. 1) with metal-dependent nucleosynthesis yields of 1) core-collapse supernovae for massive stars (Kobayashi et al. 2006), 2) thermonuclear supernovae from low-mass binary stars with the metallicity effect (Kobayashi et al. 1998), and low-mass AGB stars (Karakas 2010). However, there is a significant scatter in the observations, and we need a realistic model.

Chemodynamical simulations - We study the formation and evolutionary histories of Milky Way-type galaxies using chemo-dynamical simulations described by Kobayashi & Nakasato (2011, Fig. 2). These incorporate Smoothed Particle Hydrodynamics (SPH) to describe hydrodynamics, and direct summation with the GRAPE system or tree method describes gravity. The relevant physical processes such as radiative cooling, star formation, supernovae feedback, and chemical enrichment are all included. This enables these simulations to be compared with observed elemental abundances of stars in various locations - bulge, disk, halo, and satellite galaxies.

Galactic archaeology

B-band Luminosity Map of our simulated Milky Way-type galaxy at present for the face-on (left panel) and edge-on (right panel) projections. Each panel is 20 kpc on a side. Watch the movie on this link.

Galactic Archaeology - Using chemodynamical simulations, we have predicted the time/redshift evolution of the spatial distribution of elements from Lithium to Zinc (A=30, Fig. 3). This will be extended up to Uranium (A=92) using new AGB yields and r-process calculations. In the next decade, high-resolution multi-object spectrographs such as HERMES, APOGEE, GAIA-ESO survey, WEAVE, etc will deliver elemental abundances for million of stars in the Local Group. We aim to untangle the star formation and chemical enrichment histories using chemical evolution models and chemodynamical simulations.