Chemodynamics of a simulated disc galaxy: initial mass functions and Type Ia supernova progenitors

Abstract

We trace the formation and advection of several elements within a\ncosmological adaptive mesh refinement simulation of an L* galaxy. We use nine\nrealisations of the same initial conditions with different stellar Initial Mass\nFunctions (IMFs), mass limits for type-II and type-Ia supernovae (SNII, SNIa)\nand stellar lifetimes to constrain these sub-grid phenomena. Our code includes\nself-gravity, hydrodynamics, star formation, radiative cooling and feedback\nfrom multiple sources within a cosmological framework. Under our assumptions of\nnucleosynthesis we find that SNII with progenitor masses of up to 100 Msun are\nrequired to match low metallicity gas oxygen abundances. Tardy SNIa are\nnecessary to reproduce the classical chemical evolution knee in [O/Fe]-[Fe/H]:\nmore prompt SNIa delayed time distributions do not reproduce this feature.\nWithin our framework of hydrodynamical mixing of metals and galaxy mergers we\nfind that chemical evolution is sensitive to the shape of the IMF and that\nthere exists a degeneracy with the mass range of SNII. We look at the abundance\nplane and present the properties of different regions of the plot, noting the\ndistinct chemical properties of satellites and a series of nested discs that\nhave greater velocity dispersions, are more alpha-rich and metal poor with age.\n