agn feeding and feedback: beyond sub-grid physics andrea negrihiddenmonsters/talks/negri.pdf ·...

AGN feeding and feedback:beyond sub-grid physics

Andrea Negri

In collaboration with Marta Volonteri

Hidden Monsters: Obscured AGN and Connections to Galaxy EvolutionFriday 12 August 2016

~last decade: hydro cosmological simulations

dark matter + stars + gas

Evolution of the large scale structure

Andrea Negri – AGN feeding and feedbackIllustris simulation





Huge dynamical range!currenly impossible to simulate





Huge dynamical range!currenly impossible to simulate

Simulations are forced to adopt lower resolution

~ 6 kpc for MassiveBlack at z=0 (Di Matteo+2012)

~ 1 kpc for Horizon-AGN (Dubois+2012)

> 750 pc Illustris (10 pc hydro, Vogelsberger+14)350 pc EAGLE simulation, z=0 (Schaye+14)

need to resort to subgrid models for BH accretion

Subgrid models for BH accretion

Andrea Negri – AGN feeding and feedback


Various models are present in literature, most of them based on Bondi Bondi accretion

M BH=α4π G2 M BH

2 ρ

c s3

formal solution of: ● spherically symmetric accretion problem● adiabatic, no feedback, no rotation



Various models are present in literature, most of them based on Bondi Bondi accretion

M BH=α4π G2 M BH

2 ρ

c s3

In simulations we have:● non spherical accretion● multiphase gas● rotation

formal solution of: ● spherically symmetric accretion problem● adiabatic, no feedback, no rotation


How accretion is implemented

and cs are calculated using information on the

surrounding gas, plenty of ways (every code/author)

M BH=α4π G2 M BH

2 ρ

c s3


● Volume weighted (GADGET, Booth+09, Vogelsberger+13)● Mass weighted (Dubois+12)● ISM subgrid model (hot/cold phase, Pelupessy+07)●Global mass w. averages from all the cells (Choi+2012)●Direct accretion of hot and cold gas when hydro is more resolved than gravity (Steinborn+15)

Sometimes it is not even mentioned!


and cs are calculated using information on the

surrounding gas, plenty of ways (every code/author)

M BH=α4π G2 M BH

2 ρ

c s3


● Volume weighted (GADGET, Booth+09, Vogelsberger+13)● Mass weighted (Dubois+12)● ISM subgrid model (hot/cold phase, Pelupessy+07)●Global mass w. averages from all the cells (Choi+2012)●Direct accretion of hot and cold gas when hydro is more resolved than gravity (Steinborn+15)

Sometimes it is not even mentioned!

Roughly classified as● MassMass weighted

●Volume Volume weighted (SPH)


(~100-300) is a boost factor, depends on resolution and sub-grid models of ISM


M BH=α4π G2 M BH

2 ρ

c s3

● Constant (Springle+05, Dubois+12, Curtis+15)● Depends on ISM density (Booth+09, Steinborn+15)● Depends on feedback (Vogelsberger+13)●Sometimes not used (Pelupessy+07, Choi+12)●Sometimes is not even mentioned!


(~100-300) is a boost factor, depends on resolution and sub-grid models of ISM


M BH=α4π G2 M BH

2 ρ

c s3

● Constant (Springle+05, Dubois+12, Curtis+15)● Depends on ISM density (Booth+09, Steinborn+15)● Depends on feedback (Vogelsberger+13)●Sometimes not used (Pelupessy+07, Choi+12)●Sometimes is not even mentioned!

Philosophy behind Low resolution: ISM cold phase not resolved

Bondi radius not resolved●underestimated● c

s overestimated

BH accretion rate underestimatedunderestimated

Past attempts to calibrate the BH accretion by simulating the Bondi solution

has been performedwithout feedback


see Wurster+13, Elahi+16

But they used Bondi accretion to simulate Bondi solution!

Past attempts to calibrate the BH accretion by simulating the Bondi solution

has been performedwithout feedback


see Wurster+13, Elahi+16

But they used Bondi accretion to simulate Bondi solution!

What happens with feedbackfeedback?

A simple ideaA simple idea

Sims with same setup but with Bondi accretion:● Different schemes of weighting

●Different resolution

Fiducial simulations comparison with


Simulations of an isolated galaxy:

● High resolution ~ 0.1 pc0.1 pc (cold and hot phase)● Well resolvedWell resolved Bondi radius for all the T

● NoNo parametrized accretion

A simple ideaA simple idea

Sims with same setup but with Bondi accretion:● Different schemes of weighting

●Different resolution

Fiducial simulations comparison with


Simulations in a nutshell

Code: ZEUSMP (modified in Novak et al. 2011)

●2D axisymmetric

●MBH

= 3 × 107 M ☉

● Rbondi

= 0.1 pc at

T=108 K

●r from 0.1 pc to 250 kpc 0.1 pc to 250 kpc

●Mechanical Feedback Mechanical Feedback from broad absorption line (BAL) winds

● Radiative Radiative feedback

●Compton heating/cooling

●Radiative cooling




●2D axisymmetric

●MBH

= 3 × 107 M ☉

● Rbondi

= 0.1 pc at

T=108 K



● Radiative Radiative feedback

●Compton heating/cooling



fiducial model:fiducial model:BH accretion is fluxflux on the innermost

radial grid


cooling – accretion – feedback – hot bubble cycle



CHAOTIC ACCRETIONCHAOTIC ACCRETION



CHAOTIC ACCRETIONCHAOTIC ACCRETION

Feedback self-limits accretion to sub-Eddington values


What happens with Bondi?

1)Define accretion radius racc

2) Calculate and cs inside r

acc

3) no boost factor

Computational grid





acc

3) no boost factor

Computational grid

● High vs low resolution runs





acc

3) no boost factor

Computational grid

● High vs low resolution runs● Mass vs Volume weighted


Bondi low resolution mass weightedNO AGN

The central resolution is 3, 30 and 300 pc

The expected trend is recoveredin absenceabsence of AGN feedback


Bondi low resolutionmass weighted

Explored racc

= 3, 30, 300 pc


Trend: the larger rthe larger raccacc the larger the larger MMBHBH!!


Explored racc

= 3, 30, 300 pc


Trend: the larger rthe larger raccacc the larger the larger MMBHBH!!


I was expecting the opposite! Why?

Explored racc

= 3, 30, 300 pc

Sims with large racc

there is a stronger stronger feedback feedback but a

larger gaslarger gas mass to heat/sweep away tostop the accretion


Bondi high resolution

Sims with large racc

there is a stronger stronger feedback feedback but a

larger gaslarger gas mass to heat/sweep away tostop the accretion


Bondi high resolution

At small racc

the AGN feedback is more effective in stopping the accretion

Again, at low resolution the AGN feedback isless efficient

Compensates the fact that the accretion is dominated by hot modehot mode


Bondi low resolutionvolume weighted

Again, at low resolution the AGN feedback isless efficient

Compensates the fact that the accretion is dominated by hot modehot mode


Bondi low resolutionvolume weighted

How you calculate density and T mattersmatters!


Mass weighted sims


Volume weighted sims


Take home points● At high resolution high oscillating BH accretion: self-limitedself-limited evolution, kept sub-Eddington without artificial limiters

● The common assumption of low resolution = low accretion is not verified not verified in presence of feedback

● EfficencyEfficency of (mechanical) feedback in stopping accretion is low at low resolutionlow at low resolution

●Accretion boosting Accretion boosting is justified only with volume weighted algorithms (SPH and Illustris simulation) but you need to be very careful!

●alpha is resolution and problem dependant

Additional slides



●2D axisymmetric

●Spherical coordinates


●NO gas self-gravity (important in 3D)

●SN Ia & SNII


●Star formation (KS prescription)

●Compton heating/cooling, radiation pressure



●Spherical stellar population (Jaffe model) Reff = 5,3 kpc M

star = 3 × 1010 M☉

●BH potential well MBH

=3 × 107 M☉

+ Singular Isothermal Sphere (vc=150 km/s)

●Initial ISM density profile: flat at low r, at large radii r -2

●Two different central ISM density: 1 and 0.01 cm -3

● (Almost) no rotation

Initial conditions



star = 3 × 1010 M☉


=3 × 107 M☉





Initial conditions


MBH

= 3 × 107 M ☉ with 0.1 pc resolution

we are able to resolve the Bondi radius up to T = 108 K


star = 3 × 1010 M☉


=3 × 107 M☉





Initial conditions


BH accretion is computed as the fluxflux on the innermost radial grid

MBH

= 3 × 107 M ☉ with 0.1 pc resolution

we are able to resolve the Bondi radius up to T = 108 K

agn feeding and feedback: beyond sub-grid physics andrea negrihiddenmonsters/talks/negri.pdf ·...

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