Exploring the evolution of a dwarf spheroidal galaxy with SPH simulations: II. AGN feedback

TL;DR

This study uses SPH simulations to explore how intermediate-mass black holes influence star formation and galaxy evolution in dwarf spheroidals, revealing that AGN feedback can both suppress and enhance star formation under certain conditions.

Contribution

It provides the first detailed simulation analysis of AGN feedback effects in dwarf spheroidal galaxies, highlighting its potential to alter star formation history and galaxy evolution.

Findings

AGN feedback can both positively and negatively affect star formation.

Black hole seeds show limited growth in isolated dwarf galaxies.

AGN feedback has measurable but modest effects compared to stellar feedback.

Abstract

We investigate AGN feedback from an intermediate-mass black hole at the center of a dwarf spheroidal galaxy, by performing isolated galaxy simulations using a modified version of the GADGET-3 code. We consider Leo II (PGC 34176) in the Local Group as our simulation reference model. Beginning with black hole seeds ranging from $10^3$ to $10^6$ M$_{\odot}$, our simulations focus on comparing stellar-only feedback with AGN+stellar/SN feedback over 13.7 Gyr of galactic evolution. Our results indicate that a low-mass AGN in a dwarf galaxy influences the star formation history under specific physical conditions. While AGN feedback is generally negative on star formation, instances of positive feedback were also identified. Despite measurable effects on the evolution of the dwarf host galaxy, black hole seeds exhibited only marginal growth. We tested several physical scenarios as modified models in our simulations, primarily concerning the dynamics of the central black holes, which may wander within dwarf galaxies rather than being centrally located. However, none of these adjustments significantly impacted the growth of the black hole seeds. This suggests that intermediate-mass black holes may struggle to achieve higher masses in isolated environments, with mergers and interactions likely playing crucial roles in their growth. Nevertheless, AGN feedback exhibited non-negligible effects in our simulated dwarf spheroidal galaxies, despite the assumed dominant role of stellar feedback in the low-mass regime.