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A black hole comes back to life

Submitter: Ilse van Bemmel
Description: A team of radio astronomers, led by Megan Argo of the Jodrell Bank Centre for Astrophysics, and JIVE astronomer Ilse van Bemmel, has for the first time found evidence of the onset of a new phase of nuclear activity. The activity is associated with the central black hole in the polar ring galaxy NGC 660 (right image).

First indications of a change in NGC 660 were found during an Arecibo survey in 2012. NGC660 increased significantly in radio brightness, but the cause was unknown. The team led by Argo and van Bemmel has combined new observations from the Westerbork, e-MERLIN and EVN radio telescopes with archival results from ground- and space-based telescopes. All evidence points to a new activity phase being triggered.

The EVN data (left image) reveal a new, bright radio source at the location of the black hole. It has the typical core-jet structure associated with nuclear activity. The e-MERLIN observations show a spectral energy distribution typical for a very young active nucleus. Compared to observations from before 2010, the core of NGC 660 is several hundred times brighter, but the latest observations show that it is fading and may disappear over the next decade.

The Westerbork observations are used to study the kinematics of neutral hydrogen along the line of sight to the new radio source. The results indicate there is cold gas close to the center, a potential reservoir of fuel for this new phase of nuclear activity.

The paper: A new period of activity in the core of NGC 660, M.K. Argo, I.M. van Bemmel, S.D. Connolly & R.J. Beswick, MNRAS, in press, arXiv 1508.01781
Also see the JIVE press release
Copyright: Megan Argo, Ilse van Bemmel
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