Low frequency observations of linearly polarized structures in the interstellar medium near the south Galactic pole
Creators: name: Lenc, Emil
name: Gaensler, B. M.
name: Sun, X. H.
name: Sadler, E. M.
name: Willis, A. G.
name: Barry, N.
name: Beardsley, A. P.
name: Bell, M. E.
name: Bernardi, G.
name: Bowman, J. D.
name: Briggs, F.
name: Callingham, J. R.
name: Cappallo, R. J.
name: Carroll, P.
name: Corey, B. E.
name: de Oliveira-Costa, A.
name: Deshpande, A. A.
name: Dillon, J. S.
name: Dwarkanath, K. S.
name: Emrich, D.
name: Ewall-Wice, A.
name: Feng, L.
name: For, B. -Q.
name: Goeke, R.
name: Greenhill, L. J.
name: Hancock, P.
name: Hazelton, B. J.
name: Hewitt, J. N.
name: Hindson, L.
name: Hurley-Walker, N.
name: Johnston-Hollitt, M.
name: Jacobs, D. C.
name: Kapinska, A. D.
name: Kaplan, D. L.
name: Kasper, J. C.
name: Kim, H. -S.
name: Kratzenberg, E.
name: Line, J.
name: Loeb, A.
name: Lonsdale, C. J.
name: Lynch, M. J.
name: McKinley, B.
name: McWhirter, S. R.
name: Mitchell, D. A.
name: Morales, M. F.
name: Morgan, E.
name: Morgan, J.
name: Murphy, T.
name: Neben, A. R.
name: Oberoi, D.
name: Offringa, A. R.
name: Ord, S. M.
name: Paul, S.
name: Pindor, B.
name: Pober, J. C.
name: Prabu, T.
name: Procopio, P.
name: Riding, J.
name: Rogers, A. E. E.
name: Roshi, A.
name: Shankar, N. Udaya
name: Sethi, S. K.
name: Srivani, K. S.
name: Staveley-Smith, L.
name: Subrahmanyan, R.
name: Sullivan, I. S.
name: Tegmark, M.
name: Thyagarajan, Nithyanandan
name: Tingay, S. J.
name: Trott, C.
name: Waterson, M.
name: Wayth, R. B.
name: Webster, R. L.
name: Whitney, A. R.
name: Williams, A.
name: Williams, C. L.
name: Wu, C.
name: Wyithe, J. S. B.
name: Zheng, Q.
Publisher: name: arXiv
Year: 2016
Subjects: subject: Astrophysics of Galaxies (astro-ph.GA)
subject: Instrumentation and Methods for Astrophysics (astro-ph.IM)
subject: FOS: Physical sciences
subject: FOS: Physical sciences

description: We present deep polarimetric observations at 154 MHz with the Murchison Widefield Array (MWA), covering 625 deg^2 centered on RA=0 h, Dec=-27 deg. The sensitivity available in our deep observations allows an in-band, frequency-dependent analysis of polarized structure for the first time at long wavelengths. Our analysis suggests that the polarized structures are dominated by intrinsic emission but may also have a foreground Faraday screen component. At these wavelengths, the compactness of the MWA baseline distribution provides excellent snapshot sensitivity to large-scale structure. The observations are sensitive to diffuse polarized emission at ~54' resolution with a sensitivity of 5.9 mJy beam^-1 and compact polarized sources at ~2.4' resolution with a sensitivity of 2.3 mJy beam^-1 for a subset (400 deg^2) of this field. The sensitivity allows the effect of ionospheric Faraday rotation to be spatially and temporally measured directly from the diffuse polarized background. Our observations reveal large-scale structures (~1 deg - 8 deg in extent) in linear polarization clearly detectable in ~2 minute snapshots, which would remain undetectable by interferometers with minimum baseline lengths &gt;110 m at 154 MHz. The brightness temperature of these structures is on average 4 K in polarized intensity, peaking at 11 K. Rotation measure synthesis reveals that the structures have Faraday depths ranging from -2 rad m^-2 to 10 rad m^-2 with a large fraction peaking at ~+1 rad m^-2. We estimate a distance of 51+/-20 pc to the polarized emission based on measurements of the in-field pulsar J2330-2005. We detect four extragalactic linearly polarized point sources within the field in our compact source survey. Based on the known polarized source population at 1.4 GHz and non-detections at 154 MHz, we estimate an upper limit on the depolarization ratio of 0.08 from 1.4 GHz to 154 MHz.
description: 32 pages, 20 figures, accepted to ApJ