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

G. Bernardi, L.J. Greenhill, D.A. Mitchell, S.M. Ord, B.J. Hazelton, B.M. Gaensler, A. De Oliveira-Costa, M.F. Morales, N.U. Shankar, R. Subrahmanyan, R.B. Wayth, E. Lenc, C.L. Williams, W. Arcus, B.S. Arora, D.G. Barnes, J.D. Bowman, F.H. Briggs, J.D. Bunton, R.J. Cappallo & 33 others B.E. Corey, A. Deshpande, L. Desouza, D. Emrich, R. Goeke, D. Herne, J.N. Hewitt, M. Johnston-Hollitt, D. Kaplan, J.C. Kasper, B.B. Kincaid, R. Koenig, E. Kratzenberg, C.J. Lonsdale, M.J. Lynch, S.R. Mcwhirter, E. Morgan, D. Oberoi, J. Pathikulangara, T. Prabu, R.A. Remillard, A.E.E. Rogers, A. Roshi, J.E. Salah, R.J. Sault, K.S. Srivani, J. Stevens, S.J. Tingay, M. Waterson, R.L. Webster, A.R. Whitney, Andrew Williams, J.S.B. Wyithe

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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 ≥ 2h30 m 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. © 2013. The American Astronomical Society. All rights reserved.
Original languageEnglish
Pages (from-to)16pp
JournalAstrophysical Journal
Volume771
DOIs
Publication statusPublished - 2013

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polarization
prototypes
sky
data integration
forward modeling
deconvolution
point spread functions
angular resolution
point sources
catalogs
point source
power spectra
coverings
low frequencies
calibration

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Bernardi, G., Greenhill, L. J., Mitchell, D. A., Ord, S. M., Hazelton, B. J., Gaensler, B. M., ... Wyithe, J. S. B. (2013). A 189 MHz, 2400 deg2 polarization survey with the murchison widefield array 32-element prototype. Astrophysical Journal, 771, 16pp. https://doi.org/10.1088/0004-637X/771/2/105
Bernardi, G. ; Greenhill, L.J. ; Mitchell, D.A. ; Ord, S.M. ; Hazelton, B.J. ; Gaensler, B.M. ; De Oliveira-Costa, A. ; Morales, M.F. ; Shankar, N.U. ; 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, Andrew ; Wyithe, J.S.B. / A 189 MHz, 2400 deg2 polarization survey with the murchison widefield array 32-element prototype. In: Astrophysical Journal. 2013 ; Vol. 771. pp. 16pp.
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title = "A 189 MHz, 2400 deg2 polarization survey with the murchison widefield array 32-element prototype",
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 ≥ 2h30 m 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. {\circledC} 2013. The American Astronomical Society. All rights reserved.",
author = "G. Bernardi and L.J. Greenhill and D.A. Mitchell and S.M. Ord and B.J. Hazelton and B.M. Gaensler and {De Oliveira-Costa}, A. and M.F. Morales and N.U. Shankar and R. Subrahmanyan and R.B. Wayth and E. Lenc and C.L. Williams and W. Arcus and B.S. Arora and D.G. Barnes and J.D. Bowman and F.H. Briggs and J.D. Bunton and R.J. Cappallo and B.E. Corey and A. Deshpande and L. Desouza and D. Emrich and R. Goeke and D. Herne and J.N. Hewitt and M. Johnston-Hollitt and D. Kaplan and J.C. Kasper and B.B. Kincaid and R. Koenig and E. Kratzenberg and C.J. Lonsdale and M.J. Lynch and S.R. Mcwhirter and E. Morgan and D. Oberoi and J. Pathikulangara and T. Prabu and R.A. Remillard and A.E.E. Rogers and A. Roshi and J.E. Salah and R.J. Sault and K.S. Srivani and J. Stevens and S.J. Tingay and M. Waterson and R.L. Webster and A.R. Whitney and Andrew Williams and J.S.B. Wyithe",
year = "2013",
doi = "10.1088/0004-637X/771/2/105",
language = "English",
volume = "771",
pages = "16pp",
journal = "The Astrophysical Journal",
issn = "0004-637X",
publisher = "IOP Publishing",

}

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 2013, 'A 189 MHz, 2400 deg2 polarization survey with the murchison widefield array 32-element prototype' Astrophysical Journal, vol. 771, pp. 16pp. https://doi.org/10.1088/0004-637X/771/2/105

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.; Shankar, N.U.; 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, Andrew; Wyithe, J.S.B.

In: Astrophysical Journal, Vol. 771, 2013, p. 16pp.

Research output: Contribution to journal › Article

TY - JOUR

T1 - A 189 MHz, 2400 deg2 polarization survey with the murchison widefield array 32-element prototype

AU - Bernardi, G.

AU - Greenhill, L.J.

AU - Mitchell, D.A.

AU - Ord, S.M.

AU - Hazelton, B.J.

AU - Gaensler, B.M.

AU - De Oliveira-Costa, A.

AU - Morales, M.F.

AU - Shankar, N.U.

AU - Subrahmanyan, R.

AU - Wayth, R.B.

AU - Lenc, E.

AU - Williams, C.L.

AU - Arcus, W.

AU - Arora, B.S.

AU - Barnes, D.G.

AU - Bowman, J.D.

AU - Briggs, F.H.

AU - Bunton, J.D.

AU - Cappallo, R.J.

AU - Corey, B.E.

AU - Deshpande, A.

AU - Desouza, L.

AU - Emrich, D.

AU - Goeke, R.

AU - Herne, D.

AU - Hewitt, J.N.

AU - Johnston-Hollitt, M.

AU - Kaplan, D.

AU - Kasper, J.C.

AU - Kincaid, B.B.

AU - Koenig, R.

AU - Kratzenberg, E.

AU - Lonsdale, C.J.

AU - Lynch, M.J.

AU - Mcwhirter, S.R.

AU - Morgan, E.

AU - Oberoi, D.

AU - Pathikulangara, J.

AU - Prabu, T.

AU - Remillard, R.A.

AU - Rogers, A.E.E.

AU - Roshi, A.

AU - Salah, J.E.

AU - Sault, R.J.

AU - Srivani, K.S.

AU - Stevens, J.

AU - Tingay, S.J.

AU - Waterson, M.

AU - Webster, R.L.

AU - Whitney, A.R.

AU - Williams, Andrew

AU - Wyithe, J.S.B.

PY - 2013

Y1 - 2013

N2 - 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 ≥ 2h30 m 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. © 2013. The American Astronomical Society. All rights reserved.

AB - 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 ≥ 2h30 m 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. © 2013. The American Astronomical Society. All rights reserved.

U2 - 10.1088/0004-637X/771/2/105

DO - 10.1088/0004-637X/771/2/105

M3 - Article

VL - 771

SP - 16pp

JO - The Astrophysical Journal

JF - The Astrophysical Journal

SN - 0004-637X

ER -

Bernardi G, Greenhill LJ, Mitchell DA, Ord SM, Hazelton BJ, Gaensler BM et al. A 189 MHz, 2400 deg2 polarization survey with the murchison widefield array 32-element prototype. Astrophysical Journal. 2013;771:16pp. https://doi.org/10.1088/0004-637X/771/2/105

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