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Serendipitous discovery of a dying Giant Radio Galaxy associated with NGC 1534, using the murchison widefield array

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Authors
Hurley-Walker, N.
Johnston-Hollitt, M.
Ekers, R.
Hunstead, R.
Sadler, E.
Hindson, L.
Hancock, P.
Bernardi, G.
Bowman, J.
Briggs, F.
Cappallo, R.
Corey, B.
Deshpande, A.
Emrich, D.
Gaensler, B.
Goeke, R.
Greenhill, L.
Hazelton, B.
Hewitt, J.
Kaplan, D.
Kasper, J.
Kratzenberg, E.
Lonsdale, C.
Lynch, Mervyn
Mitchell, D.
McWhirter, R.
Morales, M.
Morgan, E.
Oberoi, D.
Offringa, A.
Ord, S.
Prabu, T.
Rogers, A.
Roshi, A.
Shankar, U.
Srivani, K.
Subrahmanyan, R.
Tingay, Steven
Waterson, M.
Wayth, Randall
Webster, R.
Whitney, A.
Williams, A.
Williams, C.
Date
2015
Type
Journal Article

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Hurley-Walker, N. and Johnston-Hollitt, M. and Ekers, R. and Hunstead, R. and Sadler, E. and Hindson, L. and Hancock, P. et al. 2015. Serendipitous discovery of a dying Giant Radio Galaxy associated with NGC 1534, using the murchison widefield array. Monthly Notices of the Royal Astronomical Society. 447 (3): pp. 2468-2478.
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Monthly Notices of the Royal Astronomical Society
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Department of Physics and Astronomy
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This article has been accepted for publication in Monthly Notices of the Royal Astronomical Society © 2015 The Authors. Published by Oxford University Press on behalf of the Royal Astronomical Society. All rights reserved.

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Abstract

Recent observations with the Murchison Widefield Array at 185 MHz have serendipitously unveiled a heretofore unknown giant and relatively nearby (z = 0.0178) radio galaxy associated with NGC 1534. The diffuse emission presented here is the first indication that NGC 1534 is one of a rare class of objects (along with NGC 5128 and NGC 612) in which a galaxy with a prominent dust lane hosts radio emission on scales of ~700 kpc. We present details of the radio emission along with a detailed comparison with other radio galaxies with discs. NGC 1534 is the lowest surface brightness radio galaxy known with an estimated scaled 1.4-GHz surface brightness of just 0.2 mJy arcmin−2. The radio lobes have one of the steepest spectral indices yet observed: α = −2.1 ± 0.1, and the core to lobe luminosity ratio is <0.1 per cent. We estimate the space density of this low brightness (dying) phase of radio galaxy evolution as 7 × 10−7 Mpc−3 and argue that normal AGN cannot spend more than 6 per cent of their lifetime in this phase if they all go through the same cycle.