Published in
Oxford University Press (OUP), Monthly Notices of the Royal Astronomical Society, 3(447), p. 2468-2478
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Serendipitous discovery of a dying giant radio galaxy associated with NGC 1534, using the Murchison Widefield array
,
Melanie Johnston-Hollitt,
Ron Ekers,
Richard Hunstead,
Elaine M. Sadler,
Luke Hindson,
Paul Hancock ,
Gianni Bernardi,
Judd D. Bowman,
Frank Briggs,
Roger J. Cappallo,
Brian E. Corey,
Avinash A. Deshpande,
David Emrich
and other authors.
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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[superscript −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[superscript −7] Mpc[superscript −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.