We present the analysis of the magnetic field (B-field) structure of galaxies measured with far-infrared (FIR) and radio (3 and 6 cm) polarimetric observations. We use the first data release of the Survey of extragALactic magnetiSm with SOFIA of 14 nearby ( < 20 Mpc) galaxies with resolved ( 5 ″ – 18 ″ ; 90 pc–1 kpc) imaging polarimetric observations using SOFIA/HAWC+ from 53 to 214 μm. We compute the magnetic pitch-angle ( Ψ B ) profiles as a function of the galactocentric radius. We introduce a new magnetic alignment parameter (ζ) to estimate the disordered-to-ordered ratio of spiral B-fields. We find FIR and radio wavelengths to not generally trace the same B-field morphology in galaxies. The Ψ B profiles tend to be more ordered across all galactocentric radii in radio ( ζ 6 cm = 0.93 ± 0.03 ) than in FIR ( ζ 154 μ m = 0.84 ± 0.14 ). For spiral galaxies, FIR B-fields are 2%–75% more turbulent than the radio B-fields. For starburst galaxies, we find that FIR polarization is a better tracer of the B-fields along the galactic outflows than radio polarization. Our results suggest that the B-fields associated with dense, dusty, turbulent star-forming regions (those traced at FIR) are less ordered than warmer, less dense regions (those traced at radio) of the interstellar medium. The FIR B-fields seem to be more sensitive to the activity of the star-forming regions and molecular clouds within a vertical height of a few hundred parsecs in the disk of spiral galaxies than the radio B-fields.

We present a comparison of the spin parameter λR, measured in a region dominated by the galaxy disc, between 20 pairs of nearby (0.005 <  z <  0.03) seemingly isolated twin galaxies differing in nuclear activity. We find that 80−82% of the active galaxies show higher values of λR than their corresponding non-active twin(s), indicating larger rotational support in the active galactic nuclei (AGN) discs. This result is driven by the 11 pairs of unbarred galaxies, for which 100% of the AGN show larger λR than their twins. These results can be explained by a more efficient angular momentum transfer from the inflowing gas to the disc baryonic matter in the case of the active galaxies. This gas inflow could have been induced by disc or bar instabilities, although we cannot rule out minor mergers if these are prevalent in our active galaxies. This result represents the first evidence of galaxy-scale differences between the dynamics of active and non-active isolated spiral galaxies of intermediate stellar masses (1010 <  M* <  1011 M⊙) in the Universe.

Mergers are thought to be a fundamental channel for galaxy growth, perturbing the gas dynamics and the magnetic fields (B-fields) in the interstellar medium (ISM). However, the mechanisms that amplify and dissipate B-fields during a merger remain unclear. We characterize the morphology of the ordered B-fields in the multiphase ISM of the closest merger of two spiral galaxies, the Antennae galaxies. We compare the inferred B-fields using 154 μm thermal dust and 11 cm radio synchrotron emission polarimetric observations. We find that the 154 μm B-fields are more ordered across the Antennae galaxies than the 11 cm B-fields. The turbulent-to-ordered 154 μm B-field increases at the galaxy cores and star-forming regions. The relic spiral arm has an ordered spiral 154 μm B-field, while the 11 cm B-field is radial. The 154 μm B-field may be dominated by turbulent dynamos with high 12CO(1–0) velocity dispersion driven by star-forming regions, while the 11 cm B-field is cospatial with high H i velocity dispersion driven by galaxy interaction. This result shows the dissociation between the warm gas mainly disturbed by the merger, and the dense gas still following the dynamics of the relic spiral arm. We find a ∼8.9 kpc scale ordered B-field connecting the two galaxies. The base of the tidal tail is cospatial with the H i and 12CO(1–0) emission and has compressed and/or sheared 154 μm and 11 cm B-fields driven by the merger. We suggest that amplified B-fields, with respect to the rest of the system and other spiral galaxies, may be supporting the gas flow between both galaxies and the tidal tail.