Inhomogeneous Chemical Evolution of the Galaxy in the Solar Neighbourhood

Abstract

N-body numerical simulations of an inhomogeneous Galactic Chemical Evolution (GCE) of the solar neighbourhood with a high temporal resolution are presented. The solar annular ring is divided into distinct spatial grids of area ~1–2 kpc². Each grid evolves distinctly in terms of star formation and nucleosynthetic yields from numerous generations of stars. The evolution of the galaxy is simulated by considering discrete episodes of star formation. Subsequent to the evolution of the simulated stars within each grid the stellar nucleosynthetic yields are homogenized within the grid rather than the traditionally adopted criteria of homogenizing over the entire solar annular ring. This provides a natural mechanism of generating heterogeneities in the elemental abundance distribution of stars. A complex chemical evolutionary history is inferred that registers episodes of time-dependent contributions from SN II+Ib/c with respect to SN Ia. It was observed that heterogeneities can remerge even after episodes of large scale homogenizations on scales larger than the grid size. However, a comparison of the deduced heterogeneities with the observed scatter in the elemental abundances of the dwarf stars suggest only a partial match, specifically, for [Fe/H] > −0.5. The deduced heterogeneities in the case of carbon, oxygen, magnesium, silicon, sulphur, calcium and titanium can explain the observed heterogeneities for [Fe/H] < −0.5. It may not be possible to explain the entire observed spread exclusively on the basis of the inhomogeneous GCE.