Galaxy formation physics behind bar formation: A view from cosmological hydrodynamical simulations

TL;DR

This study uses cosmological simulations to explore how supernova and black hole feedback influence bar formation in Milky Way-like galaxies, revealing that feedback strength affects disc stability and bar characteristics.

Contribution

It demonstrates that supernova feedback delays bar formation and influences disc properties, while black hole feedback impacts bar strength and length, providing new insights into galaxy evolution.

Findings

Supernova feedback delays bar formation.

Stronger feedback leads to larger, more stable discs.

Bar formation criteria may fail in extreme feedback cases.

Abstract

We present a suite of zoom-in cosmological simulations of Milky Way-like galaxies with a prominent disc component and a strong bar in their centre, based on a subsample of barred galaxies from the TNG50 magneto-hydrodynamic simulation. We modify the physical models that regulate star formation, namely, supernova feedback and black hole quasar feedback, to examine how they affect the disc and bar formation. We find that, independently of the feedback prescriptions, all galaxies show a similar morphology, which is dominant in comparison with the bulge mass. The black hole quasar feedback models used in this study do not affect bar formation, although they can affect the bar strength and length. The energy released by the supernovae causes a delay in the time of bar formation and, in models with the strongest feedback, galaxies form stable discs against bar formation. This could be understood since supernova feedback influences disc and bulge assembly, resulting in discs with lower mass content, radial velocity dispersion and larger size as the supernova feedback strength increases. We study disc stability using three bar instability criteria proposed in the literature. We find that galaxies with varied supernovae and black hole quasar feedback satisfy these criteria at the moment of bar formation, except in extreme cases where the galaxy lacks or has weak supernova feedback. In these models, two of three criteria fail to forecast the existence (or absence) of a bar, probably because they do not account for the influence of a massive and compact bulge. Our findings provide insights into the physical processes behind bar formation and highlight the importance of additional conditions, other than a massive and compact disc that promote bar formation.