Title:	A 189 MHz, 2400 deg2 polarization survey with the Murchison wide field array 32-element prototype
Authors:	Bernard, G. Udaya Shankar, N. Subrahmanyan, Ravi Deshpande, A.A. Prabu, T. Roshi, Anish D. Srivani, K.S.
Keywords:	diffuse radiation ISM Magnetic fields polarization radio continuum surveys techniques interferometic
Issue Date:	Jul-2013
Publisher:	IOP Sciences for The American Astronomical Society
Citation:	The Astrophysical journal, 2013, Vol.771, p105
Abstract:	We present a Stokes I, Q and U survey at 189 MHz with the Murchison Widefield Array 32 element prototype covering 2400 deg2. 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 ~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 α >= 2h30m 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 (α, δ) = (4h, -27.°6) in terms of three-dimensional power spectra.
Description:	Restricted Access. An open-access version is available at arXiv.org (one of the alternative locations)
URI:	http://hdl.handle.net/2289/5759
ISSN:	0004-637X 1538-4357-(Online)
Alternative Location:	http://adsabs.harvard.edu/abs/2013ApJ...771..105B http://arxiv.org/abs/1305.6047 http://dx.doi.org/10.1088/0004-637X/771/2/105
Copyright:	2013 American Astronomical Society
Appears in Collections:	Research Papers (A&A)

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