A Black Hole Manifesto

Abstract

A brief overview is presented of some aspects of the study of the growth of massive black holes in active galactic nuclei. It is argued that relativistic effects described by the Kerr solution of a spinning black hole are essential and are responsible for the formation of relativistic jets. It is further asserted that when the mass accretion rate is much larger and much smaller than the Eddington rate, the accretion is adiabatic and accompanied by prodigious outflows, ultimately driven by the energy flow through the disk associated with the magnetic torque. It is conjectured that this torque is dictated by the magnetic conditions at large radius and that, typically, there is preferred radial polarity in the magnetic field that joins the disk along with freshly accreted gas at its outer boundary. The associated magnetic flux is concentrated by the inflowing gas and soon becomes dynamically dominant so that it escapes the disk, driving an MHD wind. The radial field persists all the way down to the event horizon of the black hole and supplies a large flux to the hole when the disk is thick. Consequently, rapidly spinning holes accreting rapidly or slowly should be accompanied by relativistic jets which spin down the hole. The disks associated with intermediate accretion rates should be relatively thin and spin up the hole without forming powerful jets. This model provides a qualitative interpretation of the observed cosmological evolution of AGN, whereby the black holes that form later, lose the competition with star formation and grow to smaller masses. The co-evolution of black holes and their host galaxies is briefly discussed along with the impact on the intergalactic medium.