The importance of the way in which supernova energy is distributed around young stellar populations in simulations of galaxies

TL;DR

This study investigates how different methods of distributing supernova energy in galaxy simulations affect key properties like star formation and galaxy morphology, highlighting the importance of isotropic energy distribution for realistic feedback modeling.

Contribution

The paper introduces a novel isotropic neighbor-selection algorithm for supernova feedback in galaxy simulations, demonstrating its impact on galaxy evolution outcomes.

Findings

Isotropic energy distribution enhances feedback efficiency.

Different neighbor-selection strategies significantly affect galaxy properties.

Isotropic method outperforms conventional mass-weighted selection.

Abstract

Supernova (SN) feedback plays a crucial role in simulations of galaxy formation. Because blastwaves from individual SNe occur on scales that remain unresolved in modern cosmological simulations, SN feedback must be implemented as a subgrid model. Differences in the manner in which SN energy is coupled to the local interstellar medium and in which excessive radiative losses are prevented have resulted in a zoo of models used by different groups. However, the importance of the selection of resolution elements around young stellar particles for SN feedback has largely been overlooked. In this work, we examine various selection methods using the smoothed particle hydrodynamics code SWIFT. We run a suite of isolated disk galaxy simulations of a Milky Way-mass galaxy and small cosmological volumes, all with the thermal stochastic SN feedback model used in the EAGLE simulations. We complement the original mass-weighted neighbour selection with a novel algorithm guaranteeing that the SN energy distribution is as close to isotropic as possible. Additionally, we consider algorithms where the energy is injected into the closest, least dense, or most dense neighbour. We show that different neighbour-selection strategies cause significant variations in star formation rates, gas densities, wind mass loading factors, and galaxy morphology. The isotropic method results in more efficient feedback than the conventional mass-weighted selection. We conclude that the manner in which the feedback energy is distributed among the resolution elements surrounding a feedback event is as important as changing the amount of energy by factors of a few.