A scheme to unify low-power accreting black holes

Jet-dominated accretion flows and the radio/X-ray correlation

¹ ASTRON, PO Box 2, 7990 AA Dwingeloo, The Netherlands
² Adjunct Professor, Astronomy Department, University of Nijmegen, Postbus 9010, 6500 GL Nijmegen, The Netherlands
³ Max-Planck-Institut für Radioastronomie, Auf dem Hügel 69, 53121 Bonn, Germany
⁴ Massachusetts Institute of Technology, Center for Space Research, 77 Massachusetts Ave., Rm. NE80-6035, Cambridge, MA 02139, USA

Corresponding author: H. Falcke, falcke@astron.nl

Received: 20 May 2003
Accepted: 30 October 2003

Abstract

We explore the evolution in power of black holes of all masses, and their associated jets, within the scheme of an accretion rate-dependent state transition. Below a critical value of the accretion rate all systems are assumed to undergo a transition to a state where the dominant accretion mode is optically thin and radiatively inefficient. In these significantly sub-Eddington systems, the spectral energy distribution is predicted to be dominated by non-thermal emission from a relativistic jet whereas near-Eddington black holes will be dominated instead by emission from the accretion disk. Reasonable candidates for such a sub-Eddington state include X-ray binaries in the hard and quiescent states, the Galactic Center (Sgr A*), LINERs, FR I radio galaxies, and a large fraction of BL Lac objects. Standard jet physics predicts non-linear scaling between the optically thick (radio) and optically thin (optical or X-ray) emission of these systems, which has been confirmed recently in X-ray binaries. We show that this scaling relation is also a function of black hole mass and only slightly of the relativistic Doppler factor. Taking the scaling into account we show that indeed hard and quiescent state X-ray binaries, LINERs, FR I radio galaxies, and BL Lacs can be unified and fall on a common radio/X-ray correlation. This suggests that jet domination is an important stage in the luminosity evolution of accreting black hole systems.