The giant lobes of Centaurus A observed at 118 MHz with the Murchison Widefield Array

Benjamin McKinley, Frank Briggs, Bryan Malcolm Gaensler, I Feain, Gianni Bernardi, Randall B Wayth, Melanie Johnston-Hollitt, Andre R Offringa, Wayne Arcus, David Graeme Barnes, Julie Bowman, John Bunton, Roger Cappallo, Brian E Corey, Avinash Deshpande, Ludovico deSouza, David Emrich, Robert F Goeke, Lincoln Greenhill, Bryna J HazeltonDavid Edwin Herne, Jacqueline N Hewitt, David L Kaplan, Justin C Kasper, Barton B Kincaid, Ronald Koenig, Eric Kratzenberg, Colin J Lonsdale, Mervyn John Lynch, Stephen Russell McWhirter, Daniel A Mitchell, Miguel F Morales, Edward H Morgan, Divya Oberoi, Stephen M Ord, Joseph Pathikulangara, Thiagaraj Prabu, Ronald A Remillard, Alan E E Rogers, Anish A Roshi, Joseph E Salah, Robert John Sault, Natarajan Udaya-Shankar, K S Srivani, James Stevens, Ravi Subrahmanyan, Steven John Tingay, Mark F Waterson, Rachel Lindsey Webster, Alan R Whitney, Andrew Williams, Christopher L Williams, J Stuart B Wyithe

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16 Citations (Scopus)

Abstract

We present new wide-field observations of Centaurus A (Cen A) and the surrounding region at 118MHz with the Murchison Widefield Array (MWA) 32-tile prototype, with which we investigate the spectral-index distribution of Cen A s giant radio lobes.We compare our images to 1.4 GHz maps of Cen A and compute spectral indices using temperature-temperature plots and spectral tomography. We find that the morphologies at 118MHz and 1.4 GHz match very closely apart from an extra peak in the southern lobe at 118 MHz, which provides tentative evidence for the existence of a southern counterpart to the northern middle lobe of Cen A. Our spatially averaged spectral indices for both the northern and southern lobes are consistent with previous analyses, however we find significant spatial variation of the spectra across the extent of each lobe. Both the spectral-index distribution and the morphology at low radio frequencies support a scenario of multiple outbursts of activity from the central engine. Our results are consistent with inverse-Compton modelling of radio and gamma-ray data that support a value for the lobe age of between 10 and 80 Myr.
Original languageEnglish
Pages (from-to)1286 - 1301
Number of pages16
JournalMonthly Notices of the Royal Astronomical Society
Volume436
Issue number2
DOIs
Publication statusPublished - 2013

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