FNWI --- IMAPP Department of Astrophysics
Radboud University > Faculty of Science > Department of Astrophysics

Fundamental plane and Black hole unification

Supermassive black holes are thought to exist in the centers of galaxies. If the black hole accretes matter, it can be observed as an active galactic nuclus (AGN). Black holes do not only exist as supermassive black holes (millions of solar masses), they are also found in stellar X-ray binaries (XRBs), which harbor black holes of the order of 10 solar masses. The central engine of both types consists of the black holes, an accretion disc surrounded by a corona and a relativistic jet. It has recently been found that the central engine of all accreting objects is essentially scale invariant; the basic ingredients, especially the interplay between the accretion disc and the jet are similar in all cases. This scale invariance has been shown using a number of empirical correlations.

The first, the so called fundamental plane of black hole activity is an empirical correlation connecting XRBs and AGN. It is a plane in the space given by the black hole mass, the radio luminosity and the X-ray luminosity. If one restricts this correlation to only low luminosity objects, the correlation shows only little scatter.

One can also connect both classes of accreting black holes using variability properties: If one studies the characteristic timescales of black hole accretion, one also find a plane in a similar manner as the fundamental plane of black holes: Here, the space is given by the accretion rate, the black hole mass and the characteristic timescale.

The connections found can now be used to establish synergies between AGN and XRB research. For example one can use accretion models developed in XRBs for AGN feedback or study the tidal disruption of stars by supermassive black holes.