A VLA Polarimetric Study of the Galactic Center Radio Arc: Characterizing Polarization, Rotation Measure, and Magnetic Field Properties

The Radio Arc is one of the brightest systems of nonthermal filaments (NTFs) in the Galactic Center, located near several prominent H ii regions (Sickle and Pistol) and the Quintuplet stellar cluster. We present observations of the Arc NTFs using the S, C, and X bands of the Very Large Array interfe...

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Bibliographic Details
Published in:The Astrophysical journal 2019-10, Vol.884 (2), p.170
Main Authors: Paré, Dylan M., Lang, Cornelia C., Morris, Mark R., Moore, Hailey, Mao, Sui Ann
Format: Article
Language:English
Subjects:
Astrophysics
Elongated structure
Faraday effect
Filaments
Galactic center
Galactic rotation
Galaxy magnetic fields
H II regions
Interferometers
Interstellar synchrotron emission
Line of sight
Magnetic fields
Magnetic properties
Magnetism
Milky Way magnetic fields
Non-thermal radiation sources
Polarimetry
Polarization
Radio
Radio astronomy
Radio continuum emission
Star clusters
Very Large Array
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Summary:The Radio Arc is one of the brightest systems of nonthermal filaments (NTFs) in the Galactic Center, located near several prominent H ii regions (Sickle and Pistol) and the Quintuplet stellar cluster. We present observations of the Arc NTFs using the S, C, and X bands of the Very Large Array interferometer. Our images of total intensity reveal large-scale helical features that surround the Arc NTFs, very narrow subfilamentation, and compact sources along the NTFs. The distribution of polarized intensity is confined to a relatively small area along the NTFs. There are elongated polarized structures that appear to lack total intensity counterparts. We detect a range of rotation measure values from −1000 to −5800 rad m−2, likely caused by external Faraday rotation along the line of sight. After correcting for Faraday rotation, the intrinsic magnetic field orientation is found to generally trace the extent of the NTFs. However, the intrinsic magnetic field in several regions of the Arc NTFs shows an ordered pattern that is rotated with respect to the extent of the NTFs. We suggest this changing pattern may be caused by an additional magnetized source along the line of sight, so that we observe two field systems superposed in our observations. We suggest that the large-scale helical segments near the Radio Arc could be components of such a source causing these changes in the intrinsic magnetic field, and some variations in the polarization and rotation measure values along the NTFs.
ISSN:0004-637X
1538-4357
DOI:10.3847/1538-4357/ab45ed