Journal
ASTROPHYSICAL JOURNAL
Volume 771, Issue 2, Pages -Publisher
IOP PUBLISHING LTD
DOI: 10.1088/0004-637X/771/2/105
Keywords
diffuse radiation; ISM: magnetic fields; polarization; radio continuum: general; surveys; techniques: interferometric
Categories
Funding
- Australian Research Council [LE0775621, LE0882938]
- National Science Foundation [AST-0457585, AST-0821321, AST-0908884, AST-1008353, PHY-0835713]
- U.S. Air Force Office of Scientific Research [FA9550-0510247]
- Australian National Collaborative Research Infrastructure Strategy
- Australia India Strategic Research Fund
- Smithsonian Astrophysical Observatory
- MIT School of Science
- MIT Marble Astrophysics Fund
- Raman Research Institute
- Australian National University
- iVEC Petabyte Data Store
- NVIDIA
- International Centre for Radio Astronomy Research
- Western Australian State government
- [CE110001020]
- Division Of Astronomical Sciences
- Direct For Mathematical & Physical Scien [1008353, 1106059, 0821321] Funding Source: National Science Foundation
- Division Of Physics
- Direct For Mathematical & Physical Scien [0835713] Funding Source: National Science Foundation
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We present a Stokes I, Q and U survey at 189 MHz with the Murchison Widefield Array 32 element prototype covering 2400 deg(2). The survey has a 15.6 arcmin angular resolution and achieves a noise level of 15 mJy beam(-1). We demonstrate a novel interferometric data analysis that involves calibration of drift scan data, integration through the co-addition of warped snapshot images, and deconvolution of the point-spread function through forward modeling. We present a point source catalog down to a flux limit of 4 Jy. We detect polarization from only one of the sources, PMN J0351-2744, at a level of 1.8% +/- 0.4%, whereas the remaining sources have a polarization fraction below 2%. Compared to a reported average value of 7% at 1.4 GHz, the polarization fraction of compact sources significantly decreases at low frequencies. We find a wealth of diffuse polarized emission across a large area of the survey with a maximum peak of similar to 13 K, primarily with positive rotation measure values smaller than +10 rad m(-2). The small values observed indicate that the emission is likely to have a local origin (closer than a few hundred parsecs). There is a large sky area at alpha >= 2(h)30(m) where the diffuse polarized emission rms is fainter than 1 K. Within this area of low Galactic polarization we characterize the foreground properties in a cold sky patch at (alpha, delta) = (4(h), -27 degrees.6) in terms of three-dimensional power spectra.
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