2023ApJ...952....4B

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 ($\lt 20$ Mpc) galaxies with resolved ($5^{\prime\prime} \mbox{--}18^{\prime\prime} ;$ 90 pc-1 kpc) imaging polarimetric observations using SOFIA/HAWC+ from 53 to 214 μm. We compute the magnetic pitch-angle (${{\rm{\Psi }}}_{B}$) 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 ${{\rm{\Psi }}}_{B}$ profiles tend to be more ordered across all galactocentric radii in radio (${\zeta }_{6\mathrm{cm}}\,=\,0.93\pm 0.03$) than in FIR (${\zeta }_{154\mu {\rm{m}}}=0.84\pm 0.14$). 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.