Growing and mergingmassive 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-MBH mergers

It can take up to a few Gyr for two MBHs to reach ~10-100 pc separation from beginning of halo merger

cosmic time (Gyr)

MBH dynamics – galaxy scale

Tremmel+ 2015

MBH dynamics – galaxy scale

tpair=0.3 Gyr

Tremmel+ 2017

q=0.45

MBH dynamics – galaxy scale

tpair=1.7 Gyr

Tremmel+ 2017

q=0.22

One stellar nucleus dissolves, but the other provides efficient dynamical friction: time from 1kpc to 1 pc ~15 Myr

Pfister+ 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

How do MBHs grow ?

Gas accretion vs MBH-MBH mergers

The feeding/feedback cycle

Feeding: the galaxy feeds the black hole through gas inflowsBlack 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 holeIf gas is prevented from going back to the black hole, the active black hole goes back to quiescence

1. Analytical modelsExpansion and cooling of an AGN outflow in a gas disc

Hartwig, MV, Dashyan 2017

1. Analytical modelsExpansion and cooling of an AGN outflow in a gas discIf gas cools, outflow is driven by the momentum inputIf not, adiabatic expansion

Hartwig, MV, Dashyan 2017

1. Analytical models

102

103

104

105

106

107

108

106

107

108

109

1010

Gultekin+09

1D

MB

H/M

⊙

Mhalo/M⊙

>Rvir

>0.2R0 / tff>1Myr

>0.02R0 / tff>0.1Myr

<0.02R0 / tff<0.1Myr

1D models are “bimodal”: all gas ejected or nothingSee Silk & Rees 1988; King 2000+

Hartwig, MV, Dashyan 2017

1. Analytical models

102

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108

106

107

108

109

1010

Gultekin+09

MB

H/M

⊙

Mhalo/M⊙

θ = 45°

>10Vvir>Vvir

no escape

106

107

108

109

1010

Gultekin+09

Mhalo/M⊙

θ = 30°

>10Vvir>Vvir

no escape

106

107

108

109

1010

Gultekin+09

Mhalo/M⊙

θ = 10°

>1000Vvir>100Vvir

>10Vvir>Vvir

no escape

2D models are more subtle: gas can be ejected in one direction (where density is lower) but be confined in others

Ramses: Grid-based hydro solver with mesh refinement (Teyssier 2002)

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)

Cielo, Bieri, MV+17

The feeding/feedback cycle

Jet: - hydro source term, cylindrical base, orientation can be chosen - steady density/momentum/energy flux - ρjet=0.01 ρambient  - straight beam, self-collimated by internal shocks

Turbulent, inhomogeneous interstellar medium (Wagner & Bicknell 2011)- no cooling, gravity, star formation

Cielo, Bieri, MV+17

0.5 Myr

1 Myr

1.5 Myr

5 Myr

0.5 Myr

1 Myr

1.5 Myr

5 Myr

Cielo, Bieri, MV+17

The feeding/feedback cycle

0 5 10 15 20t [Myr]

10 -2

10 -1

10 0

10 1

Inflo

w @

100

pc [M

/yr]

max46min46qso46ver46

Gas is preferentially ejected perpendicular to the disc Reverse shocks, "bouncing" pressure waves, backflows produce inflows entraining gas from the discLow-level inflows can maintain and modulate BH growth and AGN activity

Cielo, Bieri, MV+17

The feeding/feedback cycle

Feeding: the galaxy feeds the black hole through gas inflowsBlack hole feedback: the kinetic and radiative output from active black holesStellar feedback: radiation from stars and supernova explosions also inject energy and momentum

The feeding/feedback cycle in small galaxies

Small galaxies: vesc~ (Mgal/Rgal)1/2 ~ σ ~100 km/sSupernova-driven winds vSN~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 Zsun)•  initial mass of BH: - one by one - based on stellar IMF + stellar mergers

Habouzit, MV, Dubois 2017

The feeding/feedback cycle in small galaxies

How do galaxies �feed normal MBHs?

z=0 BHs and AGN (Reines & Volonteri 2015)

10 Mpccosmological 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 galaxiesStellar feedback has an inhibiting effect on BH growth in small galaxies