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

journal contribution
posted on 2023-05-17, 21:11 authored by Bernardi, G, Greenhill, LJ, Mitchell, DA, Ord, SM, Hazelton, BJ, Gaensler, BM, De Oliveira-Costa, A, Morales, MF, Shankar, NU, Subrahmanyan, R, Wayth, RB, Lenc, E, Williams, CL, Arcus, W, Arora, BS, Barnes, DG, Bowman, JD, Briggs, FH, Bunton, JD, Cappallo, RJ, Corey, BE, Deshpande, A, deSouza, L, Emrich, D, Goeke, R, Herne, D, Hewitt, JN, Johnston-Hollitt, M, Kaplan, D, Kasper, JC, Kincaid, BB, Koenig, R, Kratzenberg, E, Lonsdale, CJ, Lynch, MJ, McWhirter, SR, Morgan, E, Oberoi, D, Pathikulangara, J, Prabu, T, Remillard, RA, Rogers, AEE, Roshi, A, Salah, JE, Sault, RJ, Srivani, KS, Stevens, J, Tingay, SJ, Waterson, M, Webster, RL, Whitney, AR, Williams, A, Wyithe, JSB
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, –276) in terms of three-dimensional power spectra

History

Publication title

Astrophysical Journal

Volume

771

Article number

105

Number

105

Pagination

1-16

ISSN

0004-637X

Department/School

School of Natural Sciences

Publisher

IOP Press

Place of publication

190 North Independence Mall West, Suite 601, Phil.

Rights statement

Copyright 2013 The American Astronomical Society

Repository Status

  • Restricted

Socio-economic Objectives

Expanding knowledge in the physical sciences

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