The resolution bias: low resolution feedback simulations are better at destroying galaxies

TL;DR

This study shows that lower resolution simulations of AGN feedback tend to artificially enhance gas clearing in galaxies, mainly due to the loss of feedback-resistant high-density clumps, affecting the accuracy of galaxy evolution models.

Contribution

The paper demonstrates how numerical resolution impacts AGN feedback effectiveness and introduces artifacts, emphasizing the need for careful resolution choice in galaxy simulations.

Findings

Lower resolution increases feedback efficiency in clearing gas.

High-density clumps are washed out at low resolutions.

Resolution changes cause artifacts in AGN environment effects.

Abstract

Feedback from super-massive black holes (SMBHs) is thought to play a key role in regulating the growth of host galaxies. Cosmological and galaxy formation simulations using smoothed particle hydrodynamics (SPH), which usually use a fixed mass for SPH particles, often employ the same sub-grid Active galactic nuclei (AGN) feedback prescription across a range of resolutions. It is thus important to ask how the impact of the simulated AGN feedback on a galaxy changes when only the numerical resolution (the SPH particle mass) changes. We present a suite of simulations modelling the interaction of an AGN outflow with the ambient turbulent and clumpy interstellar medium (ISM) in the inner part of the host galaxy at a range of mass resolutions. We find that, with other things being equal, degrading the resolution leads to feedback becoming more efficient at clearing out all gas in its path. For the simulations presented here, the difference in the mass of the gas ejected by AGN feedback varies by more than a factor of ten between our highest and lowest resolution simulations. This happens because feedback-resistant high density clumps are washed out at low effective resolutions. We also find that changes in numerical resolution lead to undesirable artifacts in how the AGN feedback affects the AGN immediate environment.