Precision Pollution - The effects of enrichment yields and timing on
  galactic chemical evolution
  We present an update to the chemical enrichment component of the
smoothed-particle hydrodynamics model for galaxy formation presented in
Scannapieco et al. (2005) in order to address the needs of modelling galactic
chemical evolution in realistic cosmological environments. Attribution of the
galaxy-scale abundance patterns to individual enrichment mechanisms such as the
winds from asymptotic giant branch (AGB) stars or the presence of a prompt
fraction of Type Ia supernovae is complicated by the interaction between them
and gas cooling, subsequent star formation and gas ejection. In this work we
address the resulting degeneracies by extending our implementation to a suite
of mechanisms that encompasses different IMFs, models for yields from the
aforementioned stars, models for the prompt component of the
delay-time-distribution (DTDs) for Type Ia SNe and metallicity-dependent gas
cooling rates, and then applying these to both isolated initial conditions and
cosmological hydrodynamical zoom simulations. We find DTDs with a large prompt
fraction (such as the bimodal and power-law models) have, at z=0, similar
abundance patterns compared to the low-prompt component time distributions
(uniform or wide Gaussian models). However, some differences appear, such as
the former having systematically higher [X/Fe] ratios and narrower [O/Fe]
distributions compared to the latter, and a distinct evolution of the [Fe/H]
abundance.
