Lenc, E.Gaensler, BryanSun, XSadler, EvanWillis, A. G.Barry, NicholasBeardsley, A. P.Bell, MarjorieBernardi, G.Bowman, JasonBriggs, FlorenceCallingham, J. R.Cappallo, R. J.Carroll, P.Corey, B. E.Oliveira-Costa, A. deDeshpande, A. A.Dillon, J. S.Dwarkanath, K. S.Emrich, D.Ewall-Wice, A.Feng, L.For, B.-Q.Goeke, R.Greenhill, LincolnHancock, P.Hazelton, B. J.Hewitt, JustinaHindson, L.Hurley-Walker, N.Johnston-Hollitt, M.Jacobs, DanielKapińska, A. D.Kaplan, DanielKasper, JustinKim, Andrew Hyung-DoKratzenberg, E.Line, J.Loeb, AbrahamLonsdale, C. J.Lynch, M. J.McKinley, B.McWhirter, SarahMitchell, DanielMorales, M. F.Morgan, E.Morgan, JamesMurphy, TeresaNeben, A. R.Oberoi, D.Offringa, A. R.Ord, StephenPaul, S.Pindor, B.Pober, J. C.Prabu, T.Procopio, P.Riding, J.Rogers, AdrianneRoshi, A.2017-05-312016Lenc, E., B. M. Gaensler, X. H. Sun, E. M. Sadler, A. G. Willis, N. Barry, A. P. Beardsley, et al. 2016. “Low frequency observations of linearly polarized structures in the interstellar medium near the south Galactic pole.” The Astrophysical Journal 830 (1) (October 10): 38. doi:10.3847/0004-637x/830/1/38.1538-4357http://nrs.harvard.edu/urn-3:HUL.InstRepos:32751008We 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 >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.en-USMagnetic fieldsPolarizationTechniques: polarimetrcISM: magnetic fieldsISM: structureRadio Continuum: ISMJournal Article2017-02-1420162017-05-3110.3847/0004-637x/830/1/38