Galactic magnetic fields and hierarchical galaxy formation

TL;DR

This paper develops a framework linking galactic magnetic field evolution with galaxy formation in a cosmological context, showing how magnetic field strengths vary with galaxy properties and formation processes.

Contribution

It introduces a coupled model of magnetic field evolution and galaxy formation, highlighting the impact of galaxy properties and formation history on magnetic field strengths.

Findings

Magnetic field strength is primarily influenced by the galaxy's gas content.

Different galaxy formation models predict distinct magnetic field distributions.

Satellite and central galaxies show notable differences in magnetic field strengths.

Abstract

A framework is introduced for coupling the evolution of galactic magnetic fields sustained by the mean-field dynamo with the formation and evolution of galaxies in cold dark matter cosmology. Estimates of the steady-state strength of the large-scale and turbulent magnetic fields from mean-field and fluctuation dynamo models are used together with galaxy properties predicted by semi-analytic models of galaxy formation for a population of spiral galaxies. We find that the field strength is mostly controlled by the evolving gas content of the galaxies. Thus, because of the differences in the implementation of the star formation law, feedback from supernovae and ram-pressure stripping, each of the galaxy formation models considered predicts a distribution of field strengths with unique features. The most prominent of them is the difference in typical magnetic fields strengths obtained for the satellite and central galaxy populations as well as the typical strength of the large-scale magnetic field in galaxies of different mass.