A 189 MHz, 2400 deg2 polarization survey with the murchison widefield array 32-element prototype

Bernardi, G. ; Greenhill, L. J. ; Mitchell, D. A. ; Ord, S. M. ; Hazelton, B. J. ; Gaensler, B. M. ; de Oliveira-Costa, A. ; Morales, M. F. ; Udaya Shankar, N. ; Subrahmanyan, R. ; Wayth, R. B. ; Lenc, E. ; Williams, C. L. ; Arcus, W. ; Arora, B. S. ; Barnes, D. G. ; Bowman, J. D. ; Briggs, F. H. ; Bunton, J. D. ; Cappallo, R. J. ; Corey, B. E. ; Deshpande, A. ; deSouza, L. ; Emrich, D. ; Goeke, R. ; Herne, D. ; Hewitt, J. N. ; Johnston-Hollitt, M. ; Kaplan, D. ; Kasper, J. C. ; Kincaid, B. B. ; Koenig, R. ; Kratzenberg, E. ; Lonsdale, C. J. ; Lynch, M. J. ; McWhirter, S. R. ; Morgan, E. ; Oberoi, D. ; Pathikulangara, J. ; Prabu, T. ; Remillard, R. A. ; Rogers, A. E. E. ; Roshi, A. ; Salah, J. E. ; Sault, R. J. ; Srivani, K. S. ; Stevens, J. ; Tingay, S. J. ; Waterson, M. ; Webster, R. L. ; Whitney, A. R. ; Williams, A. ; Wyithe, J. S. B. (2013) A 189 MHz, 2400 deg2 polarization survey with the murchison widefield array 32-element prototype The Astrophysical Journal, 771 (2). Article ID 105-16 pages. ISSN 0004-637X

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Official URL: http://iopscience.iop.org/article/10.1088/0004-637...

Related URL: http://dx.doi.org/10.1088/0004-637X/771/2/105


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.

Item Type:Article
Source:Copyright of this article belongs to American Astronomical Society.
Keywords:Diffuse Radiation; ISM: Magnetic Fields; Polarization; Radio Continuum: General; Surveys; Techniques: Interferometric
ID Code:114276
Deposited On:21 May 2018 05:20
Last Modified:21 May 2018 05:20

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