Momentum Driving: Which Physical Processes Dominate Active Galactic Nucleus Feedback?

Abstract

The deposition of mechanical feedback from a supermassive black hole (SMBH) in an active galactic nucleus (AGN) into the surrounding galaxy occurs via broad-line winds which must carry mass and radial momentum as well as energy. The effect can be summarized by the dimensionless parameteris the efficiency by which accreted matter is turned into wind energy in the disc surrounding the central SMBH. The outflowing mass and momentum are proportional to η, and many prior treatments have essentially assumed that η = 0. We perform one-and two-dimensional simulations and find that the growth of the central SMBH is very sensitive to the inclusion of the mass and momentum driving but is insensitive to the assumed mechanical efficiency. For example in representative calculations, the omission of momentum and mass feedback leads to an hundred fold increase in the mass of the SMBH to over 10 10 M ⊙ . When allowance is made for momentum driving, the final SMBH mass is much lower and the wind efficiencies which lead to the most observationally acceptable results are relatively low with ǫ w 10 −4 .

Two-dimensional inflow-wind solution of black hole accretion with an evenly symmetric magnetic field

“…Wind is not only a fundamental aspect of accretion flow, but also plays an important role in AGN feedback, since wind can suppress the star formation and black hole growth effectively (e.g., Ostriker et al 2010). The study of wind was initiated by the hydrodynamical and MHD numerical simulations of accretion flows (Stone, 2001).…”

Suppressing star formation in quiescent galaxies with supermassive black hole winds

“…3) tend to cluster and are consistent with those predicted by "fast" shock models The wind's driving mechanism likely originates in Akira's radio active galactic nucleus (AGN), which is detected in FIRST (Faint Images of the Radio Sky at Twenty-Centimeters) data with a luminosity density of L1.4 GHz = 1.6 × 10 21 W Hz −1 , and is most consistent with being a point source according to higher-resolution (1.5 ′′ ) follow-up Jansky VLA (Very Large Array) radio observations (W.R., in prep). Since this AGN lacks obvious extended radio jets, its feedback is most likely manifest in small-scale jets (< 1 kpc) or uncollimated winds 28,29 . Despite an Eddington ratio of λ = 3.9 × 10 −4 , energetics arguments show that the AGN's mechanical output (Pmech = 8.1 × 10 41 erg s −1 ) is sufficient to supply the wind's kinetic power (Ėwind ∼ 10 39 erg s −1 ; see Methods).…”

“…Since this AGN lacks obvious extended radio jets, its feedback is most likely manifest in small-scale jets (< 1 kpc) or uncollimated winds 28,29 . Despite an Eddington ratio of λ = 3.9 × 10 −4 , energetics arguments show that the AGN's mechanical output (Pmech = 8.1 × 10 41 erg s −1 ) is sufficient to supply the wind's kinetic power (Ėwind ∼ 10 39 erg s −1 ; see Methods).…”

Towards a new modelling of gas flows in a semi-analytical model of galaxy formation and evolution

“…The outflow rate (Ṁ •,out ) is linked to the effective accretion rate on the SMBH (Ṁ •,acc ) by the relation (Ostriker et al 2010)…”

“…A popular interpretation that can explain the low star formation efficiency in M h > 10 12 M haloes is based on the activity of a super massive black hole (SMBH) hosted by the galaxy (e.g. Croton et al 2006, Cattaneo et al 2006, Bower et al 2006, Malbon et al 2007, Somerville et al 2008, Ostriker et al 2010, Bower et al 2012. If a fraction of the energy produced by the accretion on the SMBH is used to heat the hot gas phase, the efficiency of the cooling process is decreased.…”