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The Galactic Magneto-ionic Medium Survey: moments of the Faraday spectra


Dickey, JM and Landecker, TL and Thomson, AJM and Wolleben, M and Sun, X and Carretti, E and Douglas, K and Fletcher, A and Gaensler, BM and Gray, A and Haverkorn, M and Hill, AS and Mao, SA and McClure-Griffiths, NM, The Galactic Magneto-ionic Medium Survey: moments of the Faraday spectra, Astrophysical Journal, 871, (1) Article 106. ISSN 0004-637X (2019) [Refereed Article]


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Copyright 2019 The American Astronomical Society

DOI: doi:10.3847/1538-4357/aaf85f


Faraday rotation occurs along every line of sight in the Galaxy; rotation measure (RM) synthesis allows a 3D representation of the interstellar magnetic field. This study uses data from the Global Magneto-Ionic Medium Survey, a combination of single-antenna spectro-polarimetric studies, including northern sky data from the Dominion Radio Astrophysical Observatory (DRAO) 26 m telescope (1270-1750 MHz) and southern sky data from the Parkes 64 m telescope (300-480 MHz). From the synthesized Faraday spectral cubes we compute the zeroth, first, and second moments to find the total polarized emission, mean RM, and RM width of the polarized emission. From DRAO first moments we find a weak vertical field directed from Galactic North to South, but Parkes data reveal fields directed toward the Sun at high latitudes in both hemispheres: the two surveys clearly sample different volumes. DRAO second moments show feature widths in Faraday spectra increasing with decreasing positive latitudes, implying that longer lines of sight encounter more Faraday rotating medium, but this is not seen at negative latitudes. Parkes data show the opposite: at positive latitudes the second moment decreases with decreasing latitude, but not at negative latitudes. Comparing first moments with RMs of pulsars and extragalactic sources and a study of depolarization together confirm that the DRAO survey samples to larger distances than the Parkes data. Emission regions in the DRAO survey are typically 700-1000 pc away, slightly beyond the scale height of the magneto-ionic medium; emission detected in the Parkes survey is entirely within the magneto-ionic disk, less than 500 pc away.

Item Details

Item Type:Refereed Article
Keywords:cosmic rays - ISM: magnetic fields - local interstellar matter - techniques: polarimetric, radio astronomy
Research Division:Physical Sciences
Research Group:Astronomical sciences
Research Field:Galactic astronomy
Objective Division:Expanding Knowledge
Objective Group:Expanding knowledge
Objective Field:Expanding knowledge in the physical sciences
UTAS Author:Dickey, JM (Professor John Dickey)
ID Code:133224
Year Published:2019
Web of Science® Times Cited:20
Deposited By:Mathematics and Physics
Deposited On:2019-06-19
Last Modified:2020-05-20
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