This content will become publicly available on August 10, 2023

Exploring metallicity-dependent rates of Type Ia supernovae and their impact on galaxy formation
Abstract Type Ia supernovae are critical for feedback and elemental enrichment in galaxies. Recent surveys like the All-Sky Automated Survey for Supernova (ASAS-SN) and the Dark Energy Survey (DES) find that the specific supernova Ia rate at z ∼ 0 may be ≲ 20 − 50 × higher in lower-mass galaxies than at Milky Way-mass. Independently, observations show that the close-binary fraction of solar-type Milky Way stars is higher at lower metallicity. Motivated by these observations, we use the FIRE-2 cosmological zoom-in simulations to explore the impact of metallicity-dependent rate models on galaxies of $M_* \sim 10^7\, \rm {M}_{\odot }-10^{11}\, \rm {M}_{\odot }$. First, we benchmark our simulated star-formation histories (SFHs) against observations, and show that assumed stellar mass functions play a major role in determining the degree of tension between observations and metallicity-independent rate models, potentially causing ASAS-SN and DES observations to agree more than might appear. Models in which the supernova Ia rate increases with decreasing metallicity ($\propto Z^{-0.5 \; \rm {to} \; -1}$) provide significantly better agreement with observations. Encouragingly, these rate increases (≳ 10 × in low-mass galaxies) do not significantly impact galaxy masses and morphologies, which remain largely unaffected except for our most extreme models. more »
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NSF-PAR ID:
10351389
Journal Name:
Monthly Notices of the Royal Astronomical Society
ISSN:
0035-8711
3. ABSTRACT We explore the effect of including progenitor mass- and metallicity-dependent yields, supernova rates and energetics on variations in elemental abundance ratios (particularly [α/Fe]) in dwarf galaxies. To understand how the scatter and overall trends in [α/Fe] are affected by including variable metal yields from a discretely sampled initial mass function, we run FIRE simulations of a dwarf galaxy (M⋆(z = 0$) \sim 10^6\rm \, M_{\odot })$ using nucleosynthetic yields from the NuGrid data base that depend on the stellar progenitor mass and metallicity. While NuGrid exhibits lower aggregate α-element production than default FIRE yields, we find that its explicit mass dependence, even when including turbulent metal diffusion, substantially widens the intrinsic scatter in the simulated [Fe/H]-[α/Fe] – a phenomenon visible in some observations of dwarf galaxies.
We use GRUMPY, a simple regulator-type model for dwarf galaxy formation and evolution, to forward model the dwarf galaxy satellite population of the Milky Way (MW) using the Caterpillar zoom-in simulation suite. We show that luminosity and distance distributions of the model satellites are consistent with the distributions measured in the DES, PS1, and SDSS surveys, even without including a model for the orphan galaxies. We also show that our model for dwarf galaxy sizes can simultaneously reproduce the observed distribution of stellar half-mass radii, r1/2, of the MW satellites and the overall r1/2–M⋆ relation exhibited by observed dwarf galaxies. The model predicts that some of the observed faint stellar systems with r1/2 < 10 pc are ultra-faint dwarf galaxies. Scaling of the stellar mass M⋆ and peak halo mass Mpeak for the model satellites is not described by a power law, but has a clear flattening of M⋆–Mpeak scaling at $M_{\rm peak}\lt 10^8\, \, M_{\odot }$ imprinted by reionization. As a result, the fraction of low mass haloes ($M_{\rm peak}\lt 10^8 \, M_{\odot }$) hosting galaxies with MV < 0 is predicted to be 50 per cent at $M_{\rm peak}\sim 3.6 \times 10^7\, \, M_{\odot }$. We find that such highmore »