paper

Double-double radio galaxies: remnants of merger of supermassive binary black holes

arXiv:astro-ph/0310045 · doi:10.1046/j.1365-8711.2003.06235.x

Abstract

The activity of active galaxy may be triggered by the merge of galaxies and present-day galaxies are probably the product of successive minor mergers. The frequent galactic merges at high redshift imply that active galaxy harbors supermassive unequal-mass binary black holes in its center at least once during its life time. In this paper, we showed that the recently discovered double-lobed FR II radio galaxies are the remnants of such supermassive binary black holes. The inspiraling secondary black hole opens a gap in the accretion disk and removes the inner accretion disk when it merges into the primary black hole, leaving a big hole of about several hundreds of Schwarzschild radius in the vicinity of the post-merged supermassive black hole and leading to an interruption of jet formation. When the outer accretion disk slowly refills the big hole on a viscous time scale, the jet formation restarts and the interaction of the recurrent jets and the inter-galactic medium forms a secondary pair of lobes. We applied the model to a particular double-lobed radio source B1834+620 and showed that the orbit of the secondary is elliptical with a typical eccentricity and the mass ratio of the secondary and the primary is $0.01 \la q \la 0.4$. The accretion disk is a standard -disk with $0.01 \la α\la 0.04$ and the ratio of disk half height and radius is . The model predicates that double-lobed radio structure forms only in FR II radio galaxies.

6 pages, 2 figures

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