Skip navigation
Skip navigation

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

Franzen, T. M. O.; Jackson, C. A.; Offringa, Andre; Ekers, R. D.; Wayth, R. B.; Bernardi, G.; Bowman, J. D.; Briggs, F.; Cappallo, R. J.; Deshpande, A. A.; Gaensler, B. M.; Greenhill, L. J.; Hazelton, B. J.; Johnston-Hollitt, M.; Kaplan, D. L.; Lonsdale, C. J.; McWhirter, S. R.; Mitchell, D. A.; Morales, M. F.; Morgan, E.; Morgan, J.; Oberoi, D.; Ord, S. M.; Prabu, T.; Seymour, N.; Udaya Shankar, N.; Srivani, K. S.; Subrahmanyan, R.; Tingay, S. J.; Trott, C. M.; Webster, R. L.; Williams, A.; Williams, C. L.

Description

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 5σ. 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...[Show more]

dc.contributor.authorFranzen, T. M. O.
dc.contributor.authorJackson, C. A.
dc.contributor.authorOffringa, Andre
dc.contributor.authorEkers, R. D.
dc.contributor.authorWayth, R. B.
dc.contributor.authorBernardi, G.
dc.contributor.authorBowman, J. D.
dc.contributor.authorBriggs, F.
dc.contributor.authorCappallo, R. J.
dc.contributor.authorDeshpande, A. A.
dc.contributor.authorGaensler, B. M.
dc.contributor.authorGreenhill, L. J.
dc.contributor.authorHazelton, B. J.
dc.contributor.authorJohnston-Hollitt, M.
dc.contributor.authorKaplan, D. L.
dc.contributor.authorLonsdale, C. J.
dc.contributor.authorMcWhirter, S. R.
dc.contributor.authorMitchell, D. A.
dc.contributor.authorMorales, M. F.
dc.contributor.authorMorgan, E.
dc.contributor.authorMorgan, J.
dc.contributor.authorOberoi, D.
dc.contributor.authorOrd, S. M.
dc.contributor.authorPrabu, T.
dc.contributor.authorSeymour, N.
dc.contributor.authorUdaya Shankar, N.
dc.contributor.authorSrivani, K. S.
dc.contributor.authorSubrahmanyan, R.
dc.contributor.authorTingay, S. J.
dc.contributor.authorTrott, C. M.
dc.contributor.authorWebster, R. L.
dc.contributor.authorWilliams, A.
dc.contributor.authorWilliams, C. L.
dc.date.accessioned2016-08-17T00:59:44Z
dc.date.available2016-08-17T00:59:44Z
dc.identifier.issn0035-8711
dc.identifier.urihttp://hdl.handle.net/1885/107205
dc.description.abstractWe 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 5σ. 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.
dc.description.sponsorshipCAJ thanks the Department of Science, Office of Premier and Cabinet, WA for their support through the Western Australian Fellowship Programme. Support for the MWA comes from the US National Science Foundation (grants AST-0457585, PHY-0835713, CAREER-0847753, and AST-0908884), the Australian Research Council (LIEF grants LE0775621 and LE0882938), the US Air Force Office of Scientific Research (grant FA9550-0510247), and the Centre for All-sky Astrophysics (an Australian Research Council Centre of Excellence funded by grant CE110001020). Support is also provided by the Smithsonian Astrophysical Observatory, the MIT School of Science, the Raman Research Institute, the Australian National University, and the Victoria University of Wellington (via grant MED-E1799 from the New Zealand Ministry of Economic Development and an IBM Shared University Research Grant). The Australian Federal government provides additional support via the Commonwealth Scientific and Industrial Research Organization (CSIRO), National Collaborative Research Infrastructure Strategy, Education Investment Fund, and the Australia India Strategic Research Fund, and Astronomy Australia Limited, under contract to Curtin University.
dc.publisherOxford University Press
dc.rightshttp://www.sherpa.ac.uk/romeo/issn/0035-8711/..."author can archive publisher's version/PDF" from SHERPA/RoMEO site (as at 17/08/16).
dc.rightsThis article has been accepted for publication in Monthly Notices of the Royal Astronomical Society ©: 2016 The Authors Published by Oxford University Press on behalf of the Royal Astronomical Society. All rights reserved.
dc.sourceMonthly Notices of the Royal Astronomical Society
dc.subjectmethods: data analysis
dc.subjectcatalogues
dc.subjectsurveys
dc.subjectgalaxies: active
dc.subjectradio continuum: galaxies
dc.titleThe 154 MHz radio sky observed by the Murchison Widefield Array: noise, confusion and first source count analyses
dc.typeJournal article
local.identifier.citationvolume459
dc.date.issued2016-04-13
local.identifier.ariespublicationU3488905xPUB20381
local.publisher.urlhttp://www.oxfordjournals.org/en/
local.type.statusPublished Version
local.contributor.affiliationBriggs, F., College of Physical and Mathematical Sciences, The Australian National University
dc.relationhttp://purl.org/au-research/grants/arc/CE1101020
dc.relationhttp://purl.org/au-research/grants/arc/LE0775621
dc.relationhttp://purl.org/au-research/grants/arc/LE0882938
local.bibliographicCitation.issue3
local.bibliographicCitation.startpage3314
local.bibliographicCitation.lastpage3325
local.identifier.doi10.1093/mnras/stw823
dcterms.accessRightsOpen Access
CollectionsANU Research Publications

Download

File Description SizeFormat Image
01_Franzen_The_154_MHz_Radio_Sky_2016.pdf3.33 MBAdobe PDFThumbnail


Items in Open Research are protected by copyright, with all rights reserved, unless otherwise indicated.

Updated:  19 May 2020/ Responsible Officer:  University Librarian/ Page Contact:  Library Systems & Web Coordinator