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|Title:||A 189 MHz, 2400 deg2 polarization survey with the Murchison wide field array 32-element prototype|
Udaya Shankar, N.
Roshi, Anish D.
|Keywords:||diffuse radiation ISM|
polarization radio continuum
|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)|
|Copyright:||2013 American Astronomical Society|
|Appears in Collections:||Research Papers (A&A)|
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