Andrei Lobanov (Max-Planck-Institut fuer Radioastronomie)

Binary black holes and nuclear activity in galaxies in the context of galaxy evolution - Andrei Lobanov Colloquium

ATNF Marsfield Lecture Theatre

Abstract

Nuclear activity in galaxies is a complex phenomenon regulated by a
number of factors and closely connected to mergers of galaxies. A
galactic merger perturbs substantially the dynamics of gas and stars
and leads, in most cases, to formation of a supermassive binary black
hole in the center of mass of the galaxies merged. The subsequent
dynamic evolution of the binary affects strongly the observed
properties of AGN, and it can be brought in the cosmological context
of galaxy evolution. In this framework, different classes of AGN can
be generally related to four different evolutionary stages in a binary
SMBH: 1) an early merger stage; 2) a wide pair stage; 3) a close pair
stage; and 4) a coalescence stage. Most importantly, the peak
magnitude of the nuclear activity can be connected with the primary
parameters of a BBH system: the mass ratio and orbital separation of
the two black holes. This connection enables predicting correctly the
relative fractions of different types of AGN and explaining the
relation between the galactic types and the strength of the nuclear
activity. The advent of the next generation astrophysical facilities
(such as LOFAR and SKA in the radio, JWST and ELTs in the optical,
CONSTELLATION-X in the X-ray and LISA in the gravitational wave
regimes) should make this approach a prime tool for understanding the
relation between binary black holes and cosmological evolution of
galaxies and galactic nuclei.