Kinetic or thermal AGN feedback in simulations of isolated and merging disc galaxies calibrated by the M-σ relation

Abstract

We investigate two modes of coupling the feedback energy from a central AGN to the neighbouring gas in galaxy simulations: kinetic -velocity boost, and thermal -heating. We formulate kinetic feedback models for energy-driven wind (EDW) and momentum-driven wind (MDW), using two free parameters: feedback efficiency ǫ f , and AGN wind velocity v w . A novel numerical algorithm is implemented in the SPH code GADGET-3, to prevent the expansion of a hole in the gas distribution around the BH. We perform simulations of isolated evolution and merger of disk galaxies, of Milky-Way mass as well as lower and higher masses. We find that in the isolated galaxy BH kinetic feedback generates intermittent bipolar jet-like gas outflows. We infer that current prescriptions for BH subgrid physics in galaxy simulations can grow the BH to observed values even in an isolated disk galaxy. The BH growth is enhanced in a galaxy merger, which consequently requires different model parameters to fit the observations than an isolated case. Comparing the [M BH − σ ⋆ ] relation obtained in our simulations with observational data, we conclude that it is possible to find parameter sets for a fit in all the models (e.g. v w = 10000 km/s and ǫ f = 0.25 for BH kinetic EDW), except for the case with MDW feedback in a galaxy merger, in which the BH is always too massive. The BH thermal feedback implementation of within the multiphase star-formation model is found to have negligible impact on gas properties; and the effect claimed in all previous studies is attributed to gas depletion around the BH by the creation of an artificial hole. The BH mass accretion rate in our simulations exhibit heavy fluctuations. The star formation rate is quenched with feedback by removal of gas. The circumgalactic medium (CGM) gas at galactocentric distances (20 − 100)h −1 kpc are found to give the best metallicity observational diagnostic to distinguish between BH models.

Quasar outflows at z ≥ 6: the impact on the host galaxies

“…BH accretion is numerically implemented in the GADGET-3 code using a stochastic methodology to swallow neighbouring gas particles (originally from , as described in Barai et al (2014Barai et al ( , 2016.…”

“…The BH feedback energy is distributed in the kinetic form (introduced in Barai et al 2014Barai et al , 2016, as energy-driven wind) only, and no thermal feedback is included. Surrounding gas is driven outward at a velocity vw and mass outflow rateṀw.…”

Quantifying AGN-driven metal-enhanced outflows in chemodynamical simulations

“…The detailed mechanism of this metal transport has not been well studied yet (e.g. Barai et al 2014). Direct observations of outflows from AGN (e.g.…”

Kinetic AGN feedback effects on cluster cool cores simulated using SPH

“…Note that Barai et al (2014) saw a direct proportionality of MBH with vw, for kinetic feedback in isolated galaxies and mergers. This is analytically expected because on increasing vw, Mw decreases (inverse proportionality in Eq.…”

“…Here the BH kicks out central gas within a cluster atmo- sphere, and at later times some of the ejected gas falls back in, after slowing down by interacting with the further-out intracluster gas. Whereas in Barai et al (2014), once the kicked gas escaped the galaxy, it never came back.…”