Kavli Affiliate: Susan E. Clark
| First 5 Authors: Sergio Martin-Alvarez, Enrique Lopez-Rodriguez, Tara Dacunha, Susan E. Clark, Alejandro S. Borlaff
| Summary:
The structure of magnetic fields in galaxies remains poorly constrained,
despite the importance of magnetism in the evolution of galaxies. Radio
synchrotron and far-infrared (FIR) polarization and polarimetric observations
are the best methods to measure galactic scale properties of magnetic fields in
galaxies beyond the Milky Way. We use synthetic polarimetric observations of a
simulated galaxy to identify and quantify the regions, scales, and interstellar
medium (ISM) phases probed at FIR and radio wavelengths. Our studied suite of
magnetohydrodynamical cosmological zoom-in simulations features
high-resolutions (10 pc full-cell size) and multiple magnetization models. Our
synthetic observations have a striking resemblance to those of observed
galaxies. We find that the total and polarized radio emission extends to
approximately double the altitude above the galactic disk (half-intensity disk
thickness of $h_text{I radio} sim h_text{PI radio} = 0.23 pm 0.03$ kpc)
relative to the total FIR and polarized emission that are concentrated in the
disk midplane ($h_text{I FIR} sim h_text{PI FIR} = 0.11 pm 0.01$ kpc).
Radio emission traces magnetic fields at scales of $gtrsim 300$ pc, whereas
FIR emission probes magnetic fields at the smallest scales of our simulations.
These scales are comparable to our spatial resolution and well below the
spatial resolution ($<300$ pc) of existing FIR polarimetric measurements.
Finally, we confirm that synchrotron emission traces a combination of the warm
neutral and cold neutral gas phases, whereas FIR emission follows the densest
gas in the cold neutral phase in the simulation. These results are independent
of the ISM magnetic field strength. The complementarity we measure between
radio and FIR wavelengths motivates future multiwavelength polarimetric
observations to advance our knowledge of extragalactic magnetism.
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