1. A 189 MHz, 2400 deg2 POLARIZATION SURVEY WITH THE MURCHISON WIDE FIELD ARRAY 32-ELEMENT PROTOTYPE.
- Author
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BERNARDI, G., GREENHILL, L. J., MITCHELL, D. A., ORD, S. M., Hazelton, B. J., Gaensler, B. M., OLIVEIRA-COSTA, A. DE, MORALES, M. F., SHANKAR, N. UDAYA, 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., and CAPPALLO, R. J.
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INTERFEROMETRY , *OPTICAL polarization , *DECONVOLUTION (Mathematics) , *SPECTRUM analysis , *DATA analysis - 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. [ABSTRACT FROM AUTHOR]
- Published
- 2013
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