Today's Colloquium: Radio-loud AGN -- fuelling and triggering

Image may be NSFW.
Clik here to view.© Image Credits: NASA, ESA, S. Baum and C. O'Dea (RIT), R. Perley and W. Cotton (NRAO/AUI/NSF), and the Hubble Heritage Team (STScI/AURA)

There is increasing speculation that AGN are intimately linked to the evolution of their host galaxies. Not only are they triggered as galaxies build up mass through gas accretion, but they also have the potential to drive massive outflows that can directly affect galaxy evolution by heating the gas and expelling it from galaxy bulges. However, there remain considerable uncertainties about how, when and where AGN are triggered as galaxies evolve, and what the observed diversity of the AGN population can tell us about the accretion processes close the central black holes.

In this talk I will present new Gemini, VLT, Spitzer and Herschel results for the 2Jy sample of luminous, radio-loud AGN which provide key information on the triggering mechanisms and accretion processes.

The image shows a JVLA radio map of the radio galaxy Hercules A (pink) overlaid on an optical HST/WFPC3 image of the host galaxy and surrounding field (greyscale). The bubble-like structures in the south-western radio lobe suggest that the radio source activity is intermittent, and that the radio source has gone through several cycles of recent activity. Such intermittency is important in understanding the observed diversity in the radio galaxy population.