Speaker
Description
At the BRIDGCE meeting last year, I presented the technical implementation of the binary stellar evolution (BSE) code, BINARY_C, into the cosmological-scale galaxy evolution simulation, L-GALAXIES. This implementation is now fully complete, providing us with a set of comprehensive final results describing the impact of binary stars on the dust and metal evolution of galaxies (Yates et al., submitted), which I will present in this talk.
First, I will present the effect of BSE on the key scaling relations for galaxies. We have found that binaries have a negligible impact on the stellar mass function, HI mass function, and star formation rates of galaxies, iff the total mass ejected by massive stars is unchanged. This is because massive stars determine the strength of supernova feedback, which in turn regulates galaxy growth. Binaries do noticably enhance the enrichment of carbon and nitrogen through common envelope ejection, although heavier alpha elements are more affected by the choice of SN-II yields than binary effects.
Second, I will show how this new L-GALAXIES simulation reproduces the observed dust-to-metal (DTM) and dust-to-gas (DTG) ratios for galaxies back to z ~ 4, especially with binaries included and unlike many other cosmological-scale simulations. This is chiefly due to shorter dust accretion timescales in dust-rich environments. Dust masses are still under-predicted at z > 4 in L-GALAXIES however, as in most other simulations, highlighting the need for enhanced dust production at early times.
Third, on sub-galactic scales, we find very good agreement between L-GALAXIES and observed dust and metal radial profiles in galaxies at z = 0. A drop in DTM and DTG ratios is also found in diffuse, low-metallicity regions, contradicting the common assumption of universal values.
I will finish by highlighting the wide range of future avenues of investigation that are opened-up by the inclusion of BSE into cosmological-scale simulations. These include precisely tracking rare transient events, s- and r-process element production, and the complex chemistry of the Milky Way disc and stellar halo.
