Serendipitous discovery of a dying Giant Radio Galaxy associated with NGC 1534, using the Murchison Widefield Array

Kavli Affiliate: Robert Goeke

| First 5 Authors: Natasha Hurley-Walker, Melanie Johnston-Hollitt, Ron Ekers, Richard Hunstead, Elaine M. Sadler

| Summary:

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 $sim$700,kpc. We present details of
the radio emission along with a detailed comparison with other radio galaxies
with disks. NGC1534 is the lowest surface brightness radio galaxy known with an
estimated scaled 1.4-GHz surface brightness of just 0.2,mJy,arcmin$^{-2}$.
The radio lobes have one of the steepest spectral indices yet observed:
$alpha=-2.1pm0.1$, and the core to lobe luminosity ratio is $<0.1$%. We
estimate the space density of this low brightness (dying) phase of radio galaxy
evolution as $7times10^{-7}$,Mpc$^{-3}$ and argue that normal AGN cannot
spend more than 6% of their lifetime in this phase if they all go through the
same cycle.

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