Black Hole CGM Heating

Class providing models of the heating rate (in \(\mathrm{M}_\odot\) (km/s)\(^2\) Gyr\(^{-1}\)) delivered by an active galactic nucleus to the CGM of its host halo. AGN heating of the CGM is a key mechanism for quenching star formation in massive galaxies (“radio-mode” or “maintenance-mode” feedback), counterbalancing radiative cooling of the hot gas atmosphere. Implementations may couple the jet power, the wind power, or a fixed fraction of the AGN bolometric luminosity to the surrounding hot gas.

Default implementation: blackHoleCGMHeatingJetPower

Methods

heatingRate → double precision

Compute the heating rate of the CGM due to the given blackHole.

  • class(nodeComponentBlackHole) blackHole [inout]

blackHoleCGMHeatingJetPower

A black hole CGM heating class that models AGN radio-mode feedback by coupling the accretion disk jet power to the circumgalactic medium. The fraction of jet power deposited as heat in the CGM is set by the [efficiencyRadioMode] parameter.

(Default implementation)

Parameters

  • [efficiencyRadioMode] (real; default 1.0d0) — Efficiency with which radio-mode feedback is coupled to the CGM.

blackHoleCGMHeatingQuasistatic

A black hole CGM heating class that models quasi-static AGN feedback, in which the rate of energy deposited into the circumgalactic medium depends on how closely the CGM is in hydrostatic equilibrium. Specifically, the heating rate is

\[\dot{E} = \epsilon_\mathrm{coupling} \epsilon_\mathrm{heat} \dot{M}_\bullet \clight^2,\]

where \(\dot{M}_\bullet\) is the total rest mass accretion rate onto the black hole, \(\epsilon_\mathrm{heat}=\)[efficiencyHeating] is the overall coupling efficiency, and \(\epsilon_\mathrm{coupling}\) measures the extent to which the halo is in the slow (quasi-static) cooling regime:

\[\begin{split}\epsilon_\mathrm{coupling} = \left\{ \begin{array}{ll} 1 & \hbox{ if } x < 0.9 \\ y(x)^2[2 y(x) - 3]+1 & \hbox{ if } 0.9 \le x \le 1.0 \\ 0 & \hbox{ if } x > 1.0, \end{array} \right.\end{split}\]

where \(x = r_\mathrm{cool}/r_\mathrm{virial}\) and \(y(x)=[x-0.9]/[1.0-0.9]\). Heating therefore switches off smoothly as the cooling radius grows to the virial radius, i.e. as the halo leaves the slow cooling regime (see, for example, Benson and Bower 2010). No heating occurs for non-positive accretion rates.

Parameters

  • [efficiencyHeating] (real; default 1.0d-3) — The efficiency with which accretion onto a black hole heats the CGM.