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112 - C.G. Few , S. Courty , B.K. Gibson 2014
We trace the formation and advection of several elements within a cosmological adaptive mesh refinement simulation of an L* galaxy. We use nine realisations of the same initial conditions with different stellar Initial Mass Functions (IMFs), mass lim its for type-II and type-Ia supernovae (SNII, SNIa) and stellar lifetimes to constrain these sub-grid phenomena. Our code includes self-gravity, hydrodynamics, star formation, radiative cooling and feedback from multiple sources within a cosmological framework. Under our assumptions of nucleosynthesis we find that SNII with progenitor masses of up to 100 Msun are required to match low metallicity gas oxygen abundances. Tardy SNIa are necessary to reproduce the classical chemical evolution knee in [O/Fe]-[Fe/H]: more prompt SNIa delayed time distributions do not reproduce this feature. Within our framework of hydrodynamical mixing of metals and galaxy mergers we find that chemical evolution is sensitive to the shape of the IMF and that there exists a degeneracy with the mass range of SNII. We look at the abundance plane and present the properties of different regions of the plot, noting the distinct chemical properties of satellites and a series of nested discs that have greater velocity dispersions, are more alpha-rich and metal poor with age.
We highlight two research strands related to our ongoing chemodynamical Galactic Archaeology efforts: (i) the spatio-temporal infall rate of gas onto the disk, drawing analogies with the infall behaviour imposed by classical galactic chemical evoluti on models of inside-out disk growth; (ii) the radial age gradient predicted by spectrophometric models of disk galaxies. In relation to (i), at low-redshift, we find that half of the infall onto the disk is gas associated with the corona, while half can be associated with cooler gas streams; we also find that gas enters the disk preferentially orthogonal to the system, rather than in-plane. In relation to (ii), we recover age gradient troughs/inflections consistent with those observed in nature, without recourse to radial migrations.
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