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Co-evolution of Black Holes and Galaxies: Small Scales Issues. Andrés Escala Astorquiza DAS, U. de Chile. Observational Evidence for Coevolution. M BH - σ (Ferrarese & Merrit/Gebhardt et al. 2000), M BH -M bulge (Marconi & Hunt 2003) relations.

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Co-evolution of Black Holes and Galaxies: Small Scales Issues

Andrés Escala Astorquiza

DAS, U. de Chile


Observational Evidence for Coevolution

  • MBH-σ (Ferrarese & Merrit/Gebhardt et al. 2000), MBH-Mbulge (Marconi & Hunt 2003) relations.
  • Co-evolution of cosmic SFR (Madau plot) and AGN activity.
  • AGN Heating needed for Galaxy Luminosity Function (Croton et al. 06’).

MBHs must be included in Standard Hierarchical Galaxy Formation within ΛCDM Cosmology


Small Scale Issues:

  • Two basic unsolved issues that needs to be understood for a comprehensive scenario for MBH-Galaxy co-evolution are:
  • MBHs Mergers vs Last Parsec Stalling (->GW Recoil vs Three body problem).
  • MBH growth and its feedback on the environment (SF shutoff?).

Mergers of Galaxies & MBHs

(Begelman, Blandford & Rees 1980’)

Stellar loss-cone depletion by 3-body kicks implies stalling of MBH binary coalescence at sub-parsec separations.


MBHs-Disk Interactions

  • Gaseous disks are main candidates for extracting angular momentum from MBH binaries and drive the final coalescence.
  • Simulations in the literature of binary-disk interactions can be divided in 2 groups:

Escala et al. 04,05

Dotti et al. 09

Artymowicz & Lubow 94

Shi, Krolig et al. 12

tmerge ~ torb(Type I)

tmerge ~ 1000 torb(Type II)


Binary Proto-stars.

  • Different stages in the process of formation of binary stars shows different interactions with the gaseous envelopes.
  • This will not only affect their final separation but also in their final masses since accretion also varies dramatically in both cases.
  • Relevant to investigate when starts the type II stage.

Artymowicz & Lubow (1994) & more…

Boss (1984) & more …


Analytic Estimates

  • Analytical estimates for a Gap Opening Condition can be computed by comparing the timescales for closing (~∆R2/νturb) and opening (~∆L/T) a Gap.
  • Computed for torques from a Global Non-axisymmetric Density Enhancement instead from the Resonances that appears in the linear theory (not applicable for q≈1, only for q<<1).
  • Gives a criteria that can be expressed on 2 dimensionless quantities of the binary-disk system: h/rbin Mgas(<rbin)/Mbin

del Valle & Escala (2012)

Can’t be explained by Lin & Papaloizou 86’:


Are both types present in the real Universe? Probably YES

Type I interaction should be more frequent in wet mergers and Type II in dry ones:

Type I

Type II


AGN Feedback: SF Shutoff?

  • Proposed by several authors, based on simple analytical estimates of BH growth/feedback (e.g. Silk and Rees 98, King 03, Wyithe & Loeb 03, Begelman & Nath 05).
  • DiMatteo et al (2005); Hopkins et al ++++++:

However …..

  • Resolution ≈ 100 RBHinf (all BH-physics totally unresolved).
  • These simulations have almost the same assumptions that simple analytical estimates (-> do not test them).
  • A better approach is to perform smaller scale simulations that test these hypothesis.
  • An example: hypothesis of Eddington Limited growth can be exceed thru Photon Trapping (Begelman 78), Super-Eddington Atmospheres due to unstable photon-bubbles (Begelman 02; Krumholz et al 05, 09).

Mrk 573

Measuring AGN Feedback:

  • Several ongoing attempts to quantify AGN feedback in both wind & jet modes (Krongold et al. 07,10; Rupke & Veilleux 11’; Harrison et al. 12’) .
  • However, total momentum and energy observed in the outflow is still lower than required (~1/10) .
  • Energy & momentum comes in the form of ionized gas  Canthis component transfer its momentum into heating the molecular ISM and stopping SF.

If it is not feedback, what can set MBH-σ/MBH-MBulgerelations?

  • Two Possibilties:
  • No physical link between BH and Galaxies (Jahnke & Macciò 11’), relations are just a N vs N plot.
  • Such link exists and we need to look for alternatives. Any galactic problem relevant in controlling MBH growth will work.

Implicit assumption of huge number of MBH mergers!


A personal Candidate: Galactic-Scale Fueling

Unavoidable step in the growth of Massive Black Holes and it is indeed a galactic problem!

Fueling Flowchart (Wada 2004):


Transport Supersonically Turbulent Disk (Final Kpc)

BH ~ vrot 3 (Escala 06’,07’)


Mass transport in turbulent disk (assuming a power-law inertial range):

 KS Law BH α Bulge



Becerra, M.Sc. 12’

Levine et al (2008)


Motivation: fate of MBHs after Galaxy Mergers

Galaxy mergers are common events in the universe.

Each galaxy with a sizeable bulge is expected to have a MBH.

What is the fate of the BHs? Will also Coalesce?

NGC 6240


Gap Opening Condition

  • The migration timescales predicts completely different behaviours (in the two cases) in terms of an eventual coalescence.
  • Crucial to predict whether a Gap will be opened or not and apply it for different scenarios for binary MBHs/Protostars growth.
  • Since Type I disks are generally thicker and more massive than Type II ones, M and H will be parameters to explore.

Summary I

  • We have studied under which conditions the interaction of a disk with a binary will open a gap.
  • We successfully test our analytical expectations against full 3-D hydrodynamic simulations.
  • We are now in the position to predict under which scenarios we expect an efficient MBH merging.
  • Also in a position to study when starts the type II stage in binary proto-stars.

Star Formation Triggering in Disc Galaxies

Part of Fernando Becerra´s Masters Thesis (work currently in progress)


Our work

  • Explore the possibility of second parameters
  • Example: Escala (2011)

Star Formation Triggering

  • Aim: Study galactic-scale triggering of star formation.
  • In particular the role of Mrot (maximum mass scale not stabilized by rotation)
  • Compare different star formation laws: Kennicutt Law vs SFR-Mrot relation (Escala 2011).

Differences with terrestrial fluids:

  • Nontrivial Flows: on the Earth generated by solid bodies. In space also by gravitational forces, radiation field and explosions.
  • Astrophysical fluids are frequently partially ionized. Thus, electromagnetic forces can play a role in the macroscopic dynamics.

Why Numerical Simulations are so important in Astronomy

  • Most problems requires a large dynamic range (4, 5, 6 and more orders of magnitude).
  • A broad variety of physical processes involved (gravity, hydro, radiation, B, etc) in complex geometries (full 3-d).
  • HPC needed! (Software & Hardware solutions ).

Astrophysical Fluids

  • Basic Ingredients:
  • Gravity: always.
  • Hydrodynamics: gas, stars only when collisions are not negligible.
  • Many More: Radiation Fields, G.R. corrections, Chemical/Nuclear Reactions, etc. -> generally included as sub-grid physics.

Hydro Methods Used

  • Eulerian: Adaptive Mesh Refinement (AMR).
  • Lagrangian: Smooth Particle Hydrodynamics (SPH).

Methods: SPH

  • The fluid its sampled and represented by particles smoothed by a kernel W.
  • Allows any function to be expressed in terms of its values at a set of disordered points, i.e.:
  • hj is the variable smoothing length, adjusted to keep the number of neighbors N constant.


ρ(r) = Σ mj W(r-rj;hj)


adaptive spatial resolution


Methods: AMR

  • Grid-based Technique.
  • Uses a criteria for automatic increase of the resolution.
  • Criterias can be chosen to guarantee resolve: density contrast, jeans length , shocks, etc.