Mitch Begelman

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FORMATION AND GROWTH OF SUPERMASSIVE BLACK HOLE
SEEDS

• Mitch Begelman
• JILA, University of Colorado

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COLLABORATORS

• Marta Volonteri (Cambridge/Michigan)
• Martin Rees (Cambridge)

3
NEED TO EXPLAIN

• QSOs with Mgt109M? at zgt6
• Age of Universe lt 20 tSalpeter
• ?
• Eddington-limited accretion would have to
• Start early
• Be nearly continuous
• Start with MBH gt10 100 M?

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ORIGIN OF SEEDS 2 APPROACHES

• Pop III remnants
• 100 (?) M? BHs form at z20
• Sink to center of merged haloes
• Accrete gas/merge with other seeds
• Direct collapse
• Initial BH mass ?
• How is fragmentation avoided?
• Growth mainly by accretion of gas
• Problems faced by both
• angular momentum transport
• Can be exceeded?

5

• WHAT ANGULAR MOMENTUM PROBLEM?
• WHOSE LIMIT?
• EDDINGTON
• SEEDS FROM DIRECT COLLAPSE?

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Halo with slight rotation
DM
Dynamical loss of angular momentum through nested
global gravitational instabilities
BARS WITHIN BARS
(Shlosman, Frank Begelman 89)
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(No Transcript)
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Global ang. mom. transport (Bars within Bars)

• 
  M? yr-1
• 
  
• Mass distribution isothermal,
• Accumulated mass dominates for
• BWB fails at ?

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Local ang. mom. transport ( )

• 
  M? yr-1
• 
  
• viscosity parameter
• If T const. or incr. inwards,
  likely to reach center
  

FRAGMENTATION UNLIKELY TO STOP INFALL
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TEMPERATURE DEPENDENCE

• Metal-free, H2-dissociated gas falls in
• (Metal rich and/or H2 fragments?)
• Inflow rate, mass accumulation HIGH
• Infall requires H2 or pollution by Pop III
• Inflow rate, mass accumulation LOW

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WHOSE LIMIT?
SUPPOSE A SEED BH SETTLES IN THE MIDDLE OF THE
ACCUMULATED GAS
ACCUMULATED GAS
Max. BH accretion rate is for the mass
of the ENVELOPE
BH
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RAPID GROWTH OF A PREGALACTIC BH
FORMATION OF THE SEED?
QUASISTAR
ACCUMULATED GAS
Pregalactic halo
Seed BH can grow from 10 to gt105 MSol at

(Begelman, Volonteri Rees 06)
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WHAT IS A QUASISTAR?

• Self-gravitating structure laid down by infall
• Entropy small near center, increases with r
• Very different from the supermassive stars
  postulated by Hoyle and Fowler

YOUVE GOT TO BE KIDDING
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QUASISTAR PROPERTIES

• Mass m (M?) increases with time
• Core with
• Envelope
• Entropy increases outward convectively stable
• Outer radius constant
• Core radius shrinks
• Core mass 10 M? constant
• When core temp.
  
• rapid cooling by thermal neutrinos

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CORE COLLAPSE AND FORMATION OF 10-20 M? SEED BH

SUBSEQUENT ACCRETION AT EDDINGTON LIMIT FOR
QUASISTAR MASS
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CONCLUSIONS

• Angular momentum transport is fast if global
  gravitational instabilities set in (Bars within
  Bars)
• BH can grow at Eddington limit for the
  surrounding envelope, which can be
  cvcvcvcfor the BH
• Seed can form in situ from the infalling envelope
  itself (aided by ? cooling) or can be captured
  Pop III remnant