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    The 154 MHz radio sky observed by the Murchison Widefield Array: Noise, confusion, and first source count analyses

    241217_241217.pdf (3.256Mb)
    Access Status
    Open access
    Authors
    Franzen, Thomas
    Jackson, Carole
    Offringa, A.
    Ekers, Ronald
    Wayth, Randall
    Bernardi, G.
    Bowman, J.
    Briggs, F.
    Cappallo, R.
    Deshpande, A.
    Gaensler, B.
    Greenhill, L.
    Hazelton, B.
    Johnston-Hollitt, M.
    Kaplan, D.
    Lonsdale, C.
    McWhirter, S.
    Mitchell, D.
    Morales, M.
    Morgan, E.
    Morgan, J.
    Oberoi, D.
    Ord, S.
    Prabu, T.
    Seymour, Nick
    Shankar, N.
    Srivani, K.
    Subrahmanyan, R.
    Tingay, Steven
    Trott, Cathryn
    Webster, R.
    Williams, Andrew
    Williams, C.
    Date
    2016
    Type
    Journal Article
    
    Metadata
    Show full item record
    Citation
    Franzen, T. and Jackson, C. and Offringa, A. and Ekers, R. and Wayth, R. and Bernardi, G. and Bowman, J. et al. 2016. The 154 MHz radio sky observed by the Murchison Widefield Array: Noise, confusion, and first source count analyses. Monthly Notices of the Royal Astronomical Society. 459 (3): pp. 3314-3325.
    Source Title
    Monthly Notices of the Royal Astronomical Society
    DOI
    10.1093/mnras/stw823
    ISSN
    0035-8711
    School
    Department of Electrical and Computer Engineering
    Remarks

    This article has been accepted for publication in Monthly Notices of the Royal Astronomical Society ©: 2016 Published by Oxford University Press on behalf of the Royal Astronomical Society. All rights reserved.

    URI
    http://hdl.handle.net/20.500.11937/19645
    Collection
    • Curtin Research Publications
    Abstract

    © 2016 The Authors Published by Oxford University Press on behalf of the Royal Astronomical Society. We analyse a 154 MHz image made from a 12 h observation with the Murchison Widefield Array (MWA) to determine the noise contribution and behaviour of the source counts down to 30 mJy. The MWA image has a bandwidth of 30.72 MHz, a field-of-view within the half-power contour of the primary beam of 570 deg2, a resolution of 2.3 arcmin and contains 13 458 sources above 5s. The rms noise in the centre of the image is 4-5 mJy beam-1. The MWA counts are in excellent agreement with counts from other instruments and are the most precise ever derived in the flux density range 30-200 mJy due to the sky area covered. Using the deepest available source count data, we find that the MWA image is affected by sidelobe confusion noise at the ˜3.5 mJy beam-1 level, due to incompletely peeled and out-of-image sources, and classical confusion becomes apparent at ˜1.7 mJy beam-1. This work highlights that (i) further improvements in ionospheric calibration and deconvolution imaging techniques would be required to probe to the classical confusion limit and (ii) the shape of low-frequency source counts, including any flattening towards lower flux densities, must be determined from deeper ˜150 MHz surveys as it cannot be directly inferred from higher frequency data.

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