Growing and merging massive black holes Marta Volonteri Institut d Astrophysique de Paris S. Cielo (IAP) R. Bieri (MPA) Y. Dubois (IAP) M. Habouzit (Flatiron Institute) T. Hartwig (IAP) H. Pfister (IAP) M. Trebitsch (IAP) M. Tremmel (Yale University)
How do MBHs grow? Gas accretion vs MBH-MBH mergers
MBH dynamics galaxy scale MBH-MBH mergers cosmic time (Gyr) It can take up to a few Gyr for two MBHs to reach ~10-100 pc separation from beginning of halo merger Tremmel+ 2015
MBH dynamics galaxy scale t pair =0.3 Gyr q=0.45 Tremmel+ 2017
MBH dynamics galaxy scale t pair =1.7 Gyr q=0.22 Tremmel+ 2017
MBH dynamics nuclear scale When the separation of the MBHs reach the minimum resolution of the simulation cannot follow dynamics anymore è controlled re-simulations One stellar nucleus dissolves, but the other provides efficient dynamical friction: time from 1kpc to 1 pc ~15 Myr Pfister+ 2017
How do MBHs grow? Gas accretion vs MBH-MBH mergers
The feeding/feedback cycle Feeding: the galaxy feeds the black hole through gas inflows Black hole feedback: the kinetic and radiative output from active black holes A black hole grows by accreting gas and becomes active An active black hole launches winds or jets that interact with the gas of the galaxy, modulating gas accretion onto the black hole If gas is prevented from going back to the black hole, the active black hole goes back to quiescence
1. Analytical models Expansion and cooling of an AGN outflow in a gas disc
1. Analytical models Expansion and cooling of an AGN outflow in a gas disc If gas cools, outflow is driven by the momentum input If not, adiabatic expansion Hartwig, MV, Dashyan 2017
1. Analytical models M BH /M 10 8 10 7 10 6 10 5 1D 1D models are bimodal : all gas ejected or nothing See Silk & Rees 1988; King 2000+ 10 4 10 3 10 2 Gultekin+09 10 6 10 7 10 8 10 9 10 10 M halo /M >R vir >0.2R 0 / t ff >1Myr >0.02R 0 / t ff >0.1Myr <0.02R 0 / t ff <0.1Myr Hartwig, MV, Dashyan 2017
1. Analytical models 10 8 10 7 10 6 >10V vir >V vir no escape θ = 45 >10V vir >V vir no escape θ = 30 >1000V vir >100V vir >10V vir >V vir no escape θ = 10 M BH /M 10 5 10 4 10 3 10 2 Gultekin+09 10 6 10 7 10 8 10 9 10 10 Gultekin+09 10 6 10 7 10 8 10 9 10 10 Gultekin+09 10 6 10 7 10 8 10 9 10 10 M halo /M M halo /M M halo /M 2D models are more subtle: gas can be ejected in one direction (where density is lower) but be confined in others Hartwig, MV, Dashyan 2017
The feeding/feedback cycle Ramses: Grid-based hydro solver with mesh refinement (Teyssier 2002) Turbulent, inhomogeneous interstellar medium (Wagner & Bicknell 2011) - no cooling, gravity, star formation Radiation: RAMSES-RT (Rosdahl et al. 2013, Rosdahl & Teyssier 2015) - moment method to solve radiative transfer in RAMSES - radiation pressure + diffusion of multi-scattering IR radiation - reduced speed of light approximation - AGN SED with 5 photon groups, IR è UV (Bieri+16) Jet: - hydro source term, cylindrical base, orientation can be chosen - steady density/momentum/energy flux - ρ jet =0.01 ρ ambient - straight beam, self-collimated by internal shocks Cielo, Bieri, MV+17
0.5 Myr 0.5 Myr 1 Myr 1 Myr 1.5 Myr 1.5 Myr 5 Myr 5 Myr Cielo, Bieri, MV+17
The feeding/feedback cycle Inflow @100 pc [M /yr] 10 1 10 0 10-1 max46 min46 qso46 ver46 10-2 0 5 10 15 20 t [Myr] Cielo, Bieri, MV+17
The feeding/feedback cycle Gas is preferentially ejected perpendicular to the disc Reverse shocks, "bouncing" pressure waves, backflows produce inflows entraining gas from the disc Low-level inflows can maintain and modulate BH growth and AGN activity Cielo, Bieri, MV+17
The feeding/feedback cycle in small galaxies Feeding: the galaxy feeds the black hole through gas inflows Black hole feedback: the kinetic and radiative output from active black holes Stellar feedback: radiation from stars and supernova explosions also inject energy and momentum
The feeding/feedback cycle in small galaxies Small galaxies: v esc ~ (M gal /R gal ) 1/2 ~ σ ~100 km/s Supernova-driven winds v SN ~200-300 km/s Supernova feedback is sufficient to energize the gas and suppress black hole accretion (Dubois+14) Also suppress/regulate star formation, ça va sans dire.
The feeding/feedback cycle in small galaxies Ramses: Grid-based hydro solver with mesh refinement (Teyssier 2002) - Cooling/Star formation (Rasera & Teyssier 2006) - Supernova feedback (Dubois & Teyssier 2008, Teyssier et al. 2013, Dubois et al. 2015) - BH accretion + AGN feedback (Dubois et al. 2012) MBH seeds formed in: overdense bound collapsing regions metal-poor (Z<10-3.5 Z sun ) initial mass of BH: - one by one - based on stellar IMF + stellar mergers Habouzit, MV, Dubois 2017
How do galaxies feed normal MBHs? z=0 BHs and AGN (Reines & Volonteri 2015) 10 Mpc cosmological volume, ~80pc resolution Habouzit, MV, Dubois 2016
How do galaxies feed normal MBHs? Trebitsch, MV+ in prep
Growing and merging massive black holes Merging BHs are not necessarily found in merging/ disturbed galaxies beware of timescales! AGN feedback is not the main regulator of BH growth in small galaxies Stellar feedback has an inhibiting effect on BH growth in small galaxies