Open AccessCooling flows as a calorimeter of active galactic nucleus mechanical power
Author(s) -
Churazov E.,
Sunyaev R.,
Forman W.,
Böhringer H.
Publication year - 2002
Publication title -
monthly notices of the royal astronomical society
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 2.058
H-Index - 383
eISSN - 1365-2966
pISSN - 0035-8711
DOI - 10.1046/j.1365-8711.2002.05332.x
Subject(s) - physics , active galactic nucleus , accretion (finance) , radiative cooling , astrophysics , cooling flow , supermassive black hole , luminosity , black hole (networking) , galaxy , gravitational energy , gravitation , eddington luminosity , outflow , mechanical energy , astronomy , power (physics) , gravitational wave , thermodynamics , computer network , routing protocol , routing (electronic design automation) , meteorology , computer science , link state routing protocol
The assumption that radiative cooling of gas in the centres of galaxy clusters is approximately balanced by energy input from a central supermassive black hole implies that the observed X‐ray luminosity of the cooling flow region sets a lower limit on active galactic nucleus (AGN) mechanical power. The conversion efficiency of the mechanical power of the AGN into gas heating is uncertain, but we argue that it can be high even in the absence of strong shocks. These arguments inevitably lead to the conclusion that the time‐averaged mechanical power of AGNs in cooling flows is much higher than the bolometric luminosity of these objects observed currently. The energy balance between cooling losses and AGN mechanical power requires some feedback mechanism. We consider a toy model in which the accretion rate on to a black hole is set by the classic Bondi formula. Application of this model to the best studied case of M87 suggests that accretion proceeds at approximately the Bondi rate down to a few gravitational radii with most of the power (at the level of a few per cent of the rest mass) being carried away by an outflow.