Supermassive black hole quasar remnants

Studies of the cosmic X-ray background indicate that it arises mainly from accretion powered AGNs and that the present-epoch mass density in the form of supermassive black holes must be at least an order of magnitude more than represented by currently active Seyfert galactic nuclei. The black hole mass spectrum of these Seyfert nuclei extends up to ∼2×108 solar masses. Evidence summarized here suggests that much of the local mass density of compact galactic nuclei is associated with inactive quasar remnants which are now black holes that are substantially more massive than Seyfert nuclei. It is emphasized that such quasar remnant black holes are sufficiently massive to preclude the tidal disruption of any infalling stars, solar sized as well as compact. Any Keplerian orbits about these supermassive black holes would have periods exceeding 7 hours.