BINARY BLACK HOLES IN AGN - EJECTION OF STARS AND MERGING
Peter L. BIERMANN
MPI Bonn
Résumé :
Most galaxies are believed to harbour a massive black hole at their
center, and most galaxies are believed to merge with others during their
life-time, perhaps many times. Such a merger will usually lead
to a starburst at the common center of the merged galaxy. Also,
each time this happens, two black holes come close to each other, and may
merge. We show that the torque exerted by the two black holes on the star
distribution produces a belt-like configuration. Considering then the
fraction of stars with appreciable mass loss, both newly formed massive
stars, and old red giant stars, these many stellar winds are exposed to
the radiation from the central engine and will form long outward
pointed tails. We show that the sum of these tails may be optically
thick, both geometrically and also to Thomson scattering, explaining the
properties of the torus often inferred from IR and X-ray data in the
centers of Active Galactic Nuclei. The torque on the stars leads to
angular momentum loss to let the two black holes merge. The black hole
merger then leads to ubiquitous emission of gravitational waves, which
transport angular momentum. The dependence of this angular momentum loss
on the spin parameters of the two black holes and their orbit is a
challenge, relevant for gravitational wave experiments. This work was
done with Christian Zier and Mihaela Chirvasa.
