Proceedings of the International Astronomical Union

Contributed Papers

Episodic ejection from super-massive black holes

Lakshmi Saripallia1 p1, Ravi Subrahmanyana1 and Richard W. Hunsteada2

a1 Raman Research Institute, Bangalore, India email:,

a2 School of Physics, University of Sydney, Australia email:


Episodic activity in super-massive black holes is shown by radio galaxies exhibiting ‘double-double’ radio morphologies (Subrahmanyan et al. 1996, Schoenmakers et al. 2000). Spectacular examples showing a renewal of beam activity in the form of new beams emerging within relic radio lobes of previous activity have placed the phenomenon of recurrence in AGN outflows on a firm footing.

By using the SUMSS and WENSS GRG samples, we infer that on timescales of order a few million years, low luminosity radio sources are more likely to exhibit episodic behaviour in the accretion on to their supermassive black holes as compared to the more powerful radio galaxies.


  • Galaxies;
  • active – galaxies: nuclei – accretion


p1 Present address: Raman Research Institute, C. V. Raman Avenue, Sadashivanagar, Bangalore 560 080, India.