Kavli Affiliate: Mark Vogelsberger
| Summary:
It is often understood that supernova (SN) feedback in galaxies is responsible for regulating star formation (SF) and generating gaseous outflows. However, a detailed look at their small-scale effects on the interstellar medium (ISM) in simulations shows that these processes proceed in distinct and separate channels. We demonstrate this finding in two independent simulations of isolated dwarf galaxies with very high ($m_rm gas$ $sim msun$) numerical resolution, small LYRA and small RIGEL. Focusing on the immediate environment surrounding SNe, our findings suggest that the macroscopic effect of a given SN on the galaxy is best predicted by its local density. Outflows are driven by SNe in diffuse regions expanding to their cooling radii on large ($sim$ kpc) scales, while dense SF regions are disrupted in a localized ($sim$ pc) manner. However, these separate feedback channels are only distinguishable at very high resolutions capable of following mass scales $lesssim 10^2 ,msun$. When averaging on coarser scales, ISM densities are greatly mis-estimated, and variations between different SF and SNe-affected regions are severely washed out. It therefore cannot be self-consistently determined, from coarse-resolution information textitalone, (1) whether a SN tends to contribute to outflows or direct SF suppression, and (2) the rate of SF in a given region. In particular, commonly used parameters in coarse-resolution (subgrid) models, such as the SN cooling radius and SF density threshold, may require more detailed treatments informed by high-resolution studies.
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