The Role of Magnetic Fields Across the Milky Way: Polarimetry from HAWC+/SOFIA
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David Chuss
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Understanding the role and importance of interstellar magnetic fields has been a key goal in many astrophysical contexts; however, it is one that is challenging to address. Far-infrared polarimetry provides a means for measuring magnetic fields via mapping of polarized emission from magnetically-aligned dust. Observations from the High-resolution Airborne Wide-band Camera (HAWC+), a far-infrared camera for the Stratospheric Observatory for Infrared Astronomy (SOFIA), provide new capability for understanding of the role of magnetic fields in the star formation process, the physics of interstellar dust, and the magnetic environment of our Galactic center.

One of the key questions that such observations address is that of whether magnetic fields are responsible for the extremely low rate of star formation in the Milky Way. New data are enabling the measurement of the magnetic field strength and structure across environments ranging from low mass protostellar cores to regions of high mass star formation. These observations, along with the magnetohydrodynamical models that they are both testing and motivating, are revealing a story of star formation in which tenuous flows of filamentary gas, guided by magnetic fields, feed denser regions where magnetic pressure slows gravitational collapse and thereby impedes the formation of stars. 

With the continual development of new models for composition and alignment, the physics of interstellar dust is of interest across a broad range of fields from planet formation to the search for evidence of inflation in measurements of the cosmic microwave background. Multiwavelength polarimetric observations from HAWC+ are addressing such models through study of variations of the wavelength-dependence of polarization as a function of environment.

Far-infrared polarimetry has also been applied to our understanding of the role of magnetic fields in unique objects that exist in the extreme environment of our Galactic center.  HAWC+ data have explored both the magnetic implications for accretion of matter onto our central black hole and the interplay between the magnetic fields in the region’s molecular phase and those in the tenuous plasma that are traced by large, coherent non-thermal radio filaments.

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