Magnetic fields and star formation in galaxies of different morphological types

TL;DR

This study investigates how magnetic fields and star formation rates relate in different galaxy types, revealing that magnetic field structures are largely independent of star formation activity.

Contribution

It provides new insights into the nonlinear growth of magnetic fields with star formation rate and the independence of magnetic field structure from star formation activity.

Findings

Magnetic field strength grows nonlinearly with SFR.

Vertical scale heights are consistent across galaxies with different SFR.

Large-scale magnetic field configuration is independent of SFR.

Abstract

From our radio continuum and polarization observations of a sample of spiral galaxies with different morphological types, inclinations, and star formation rates (SFR) we found that galaxies with low SFR have higher thermal fractions/ smaller synchrotron fractions than those with normal or high SFR. Adopting an equipartition model, we concluded from our observations that the nonthermal radio emission and the total magnetic field strength grow nonlinearly with SFR. We also studied the magnetic field structure and disk thicknesses in highly inclined (edge-on) galaxies. We found in five galaxies that - despite their different radio appearance - the vertical scale heights for both, the thin and thick disk/halo, are about equal (0.3/1.8kpc), independently of their different SFR. They also show a similar large-scale magnetic field configuration, parallel to the midplane and X-shaped further away from the disk plane, independent of Hubble type and SFR in the disk. Hence we conclude that the amplification and formation of the large-scale magnetic field structure is independent of SFR.