Radiative efficiency, variability and Bondi accretion on to massive black holes: the transition from radio AGN to quasars in brightest cluster galaxies
By H. Russell, B. McNamara, A. Edge, M. Hogan, R. Main, A. Vantyghem, U. Waterloo, Perimeter Institute, Cfa, Durham. 2012
141 citations recorded by the source corpus.
We examine unresolved nuclear X-ray sources in 57 brightest cluster galaxies to study the relationship between nuclear X-ray emission and accretion on to supermassive black holes. The majority of the clusters in our sample have prominent X-ray cavities embedded in the surrounding hot atmospheres, which we use to estimate mean jet power and average accretion rate on to the supermassive black holes over the past several hundred Myr. We find that roughly half of the sample have detectable nuclear X-ray emission. The nuclear X-ray luminosity is correlated with average accretion rate determined using X-ray cavities, which is consistent with the hypothesis that nuclear X-ray emission traces ongoing accretion. The results imply that jets in systems that have experienced recent active galactic nucleus (AGN) outbursts, in the last ∼107 yr, are ‘on’ at least half of the time. Nuclear X-ray sources become more luminous with respect to the mechanical jet power as the mean accretion rate rises. We show that nuclear radiation exceeds the jet power when the mean accretion rate rises above a few per cent of the Eddington rate, or a power output of ∼1045ergs−1, where the AGN apparently transitions to a quasar. The nuclear X-ray emission from three objects (A2052, Hydra A, M84) varies by factors of 2–10 on time-scales of 6 months to 10 years. If variability at this level is a common phenomenon, it can account for much of the scatter in the relationship between mean accretion rate and nuclear X-ray luminosity. We find no significant change in the spectral energy distribution as a function of luminosity in the variable objects. The nuclear X-ray luminosity is consistent with emission from either a jet, an advection-dominated accretion flow, or a combination of the two, although other origins are possible. We also consider the longstanding problem of whether jets are powered by the accretion of cold circumnuclear gas or nearly spherical inflows of hot keV gas. For a subset of 13 nearby systems in our sample, we re-examine the relationship between the jet power and the Bondi accretion rate. The results indicate weaker evidence for a trend between Bondi accretion and jet power, due to uncertainties in the cavity volumes and gas densities at the Bondi radius. We suggest that cold gas fuelling could be a likely source of accretion power in these objects; however, we cannot rule out Bondi accretion, which could play a significant role in low-power jets.
Subfields: Astronomy and Astrophysics, Nuclear and High Energy Physics
View Paper: https://www.semanticscholar.org/paper/74ae2ef89e7fd14f4e96f9ac0ef9a36c6aada7bc
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Citations in the corpus
- The subarcsecond mid-infrared view of local active galactic nuclei – II. The mid-infrared–X-ray correlation (2015, unknown): “…(2009); 45: González-Martı́n et al. (2009a); 46: Younes et al. (2011); 47: Bianchi, Guainazzi & Chiaberge (2006); 48: Matt et al. (2013); 49: Guainazzi et al. (2004); 50: Awaki et al. (2000); 51: Kharb et al. (2012); 52: Russell et al. (2013); 53: Braito et al. (2009); 54: Teng et al. (in prep.)”
- Raining on black holes and massive galaxies: the top-down multiphase condensation model (2016, background): “13 in Russell et al. 2013).”
- The Coevolution of Galaxies and Supermassive Black Holes: Insights from Surveys of the Contemporary Universe (2014, background): “Even at the scale of X-ray binaries, there is ongoing debate in the literature as to whether the power of the radio jet produced depends upon the spin of the black hole (e.g. Russell et al. 2013b, Steiner et al. 2013).”
- Hot Accretion Flows Around Black Holes (2014, background): “The fact that the black holes are dim thus suggests that they must be accreting via a radiatively inefficient mode, i.e., a hot accretion flow (Fabian & Rees 1995, Di Matteo et al. 2000, Ho 2009, Russell et al. 2013b).”
- Black hole evolution – I. Supernova-regulated black hole growth (2015, background): “Though this quasar/radio mode matches the observed radiatively efficient/inefficient activities of AGN feedback (Churazov et al. 2005; Russell et al. 2013), it is possible that some accretion rate-driven jets become indistinguishable from large opening angle AGN-driven nuclear outflows after they…”