Radio Polarization from the Inner Galaxy at Arcminute Resolution

By Bryan Gaensler, J. Dickey, N. McClure-Griffiths, A. Green, M. Wieringa, Raymond Haynes Mit, U. Minnesota, U. Sydney, Atnf. 2000

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The Southern Galactic Plane Survey (SGPS) is an H I and 1.4 GHz continuum survey of the fourth quadrant of the Galaxy at arcminute resolution. We present here results on linearly polarized continuum emission from an initial 28 deg2 test region for the SGPS, consisting of 190 mosaicked pointings of the Australia Telescope Compact Array and covering the range 325.°5 < l < 332.°5, -0.°5 < b < 3.°5. Complicated extended structure is seen in linear polarization throughout the test region, almost all of which has no correlation with total intensity. We interpret the brightest regions of polarized emission as representing intrinsic structure in extended polarization, most likely originating in the Crux spiral arm at a distance of 3.5 kpc; fainter polarized structure is imposed by Faraday rotation in foreground material. Two large areas in the field are devoid of polarization. We argue that these voids are produced by foreground H II regions in which the magnetic field is disordered on scales of ~0.1-0.2 pc. We also identify a depolarized halo around the H II region RCW 94, which we suggest results from the interaction of the H II region with a surrounding molecular cloud.

Subfields: Astronomy and Astrophysics

View Paper: https://www.semanticscholar.org/paper/563a59807c5cb6abb116ecd584f21c54c03ddbe3

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An absolutely calibrated survey of polarized emission from the northern sky at 1.4 GHz. Observations (2005, background): “…and available at http://www.edpsciences.org/aa or http://dx.doi.org/10.1051/0004-6361:20053851 Survey (CGPS: Gray et al. 1998, 1999; Taylor et al. 2003; Uyaniker et al. 2003), and the Southern Galactic Plane Survey (SGPS: Gaensler et al. 2001) have angular resolution of order 1′, also at 1.4 GHz.”
Radio observational constraints on Galactic 3D-emission models (2007, background): “For the SGPS data the binning procedure is the same as used by Brown et al. (2007).”
The Southern Galactic Plane Survey: H I Observations and Analysis (2005, background): “…cool H i clouds in the inner Galaxy (Dickey et al. 2003), an examination of extended polarized emission structure and rotation measures of point sources (Gaensler et al. 2001), and an analysis of rotation measure fluctuations indicating an outer scale for turbulence of 2 pc (Haverkorn et al. 2004).”
Magnetism in the spiral galaxy NGC 6946: magnetic arms, depolarization rings, dynamo modes, and helical fields (2007, background): “…the polarization angle, resembling the canals in the λ21 cm and λ90 cm polarization maps of the Milky Way with resolutions of more than an arcminute (Gaensler et al. 2001; Uyanıker et al. 2003; Haverkorn et al. 2004) and in the λ20 cm polarization map of M 31 with 45′′ resolution (Shukurov &…”
A NEW MODEL OF THE GALACTIC MAGNETIC FIELD (2012, background): “…the Large Magellanic Cloud (Gaensler et al. 2005; Mao 2012); 160 RMs near Centaurus A (Feain et al. 2009); and 905 RMs from various other observational efforts (Simard-Normandin et al. 1981; Broten et al. 1988; Clegg et al. 1992; Oren & Wolfe 1995; Minter & Spangler 1996; Gaensler et al. 2001).”
Pulsar Rotation Measures and the Large-Scale Structure of the Galactic Magnetic Field (2006, background): “There are also many small-angular-scale structures resulting from diffuse polarized emission at different distances which are modified by foreground Faraday screens (Gaensler et al. 2001; Uyanıker & Landecker 2002; Haverkorn et al. 2003).”
Rotation Measures of Extragalactic Sources behind the Southern Galactic Plane: New Insights into the Large-Scale Magnetic Field of the Inner Milky Way (2007, methodology): “For details about the SGPS observations and polarimetric data reduction, see Gaensler et al. (2001) and Haverkorn et al. (2006b).”
Detection of polarization in the cosmic microwave background using DASI (2002, background): “These maps show much more small-scale structure in polarization than in temperature, but this is mostly induced by Faraday rotatio”
Science with the Murchison Widefield Array (2012, background): “Increasing depolarisation as a function of decreasing frequency will give independent measurements of the amount and scale of fluctuations in the magneto-ionised medium (Sokoloff et al. 1998; Gaensler et al. 2001).”