1. THE FIRST SUPERMASSIVE BLACK HOLES?
Mitch Begelman
JILA, University of Colorado

2. COLLABORATORS Marta Volonteri (Cambridge/Michigan)
Martin Rees (Cambridge)

3. COLLABORATORS Marta Volonteri (Cambridge/Michigan)
Martin Rees (Cambridge)
Elena Rossi (JILA)
Phil Armitage (JILA)

4.  NEED TO EXPLAIN: Ubiquity of BHs in present-day galaxies
QSOs with M>109M at z>6
Age of Universe < 20 tSalpeter 
Eddington-limited accretion would have to:
Start early
Be nearly continuous
Start with MBH >10 – 100 M

5. The Rees Flow Chart
Begelman & Rees, MNRAS 1978

6. One more time,
with calligraphy…
Rees, Physica Scripta, 1978

7. 18 years later… with 4-color printing!
Begelman & Rees,
“Gravity’s Fatal Attraction” 1996

8. ORIGIN OF SEEDS: 2 APPROACHES
Pop III remnants
~100 (?) M BHs form at z~20
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?

9. WHAT ANGULAR MOMENTUM PROBLEM?
WHOSE LIMIT?
EDDINGTON
SEEDS FROM DIRECT COLLAPSE?
OBSERVING SEED BH FORMATION

10. Halo with slight rotation Gas collapses ifDM
gas DM
gas
Dynamical loss of angular momentum through nested global gravitational instabilities
“BARS
WITHIN
BARS”
(Shlosman, Frank & Begelman 89)

12. WHEN IS GAS UNSTABLE? Init. collapse with conserved ang. mom.
Mestel, rigid, exponential disk
Include NFW halo potential
Vary fraction of gas collapsing, fd
Choose halo ang. mom. parameter λspin from lognormal distribution
Stability threshold: f T/W > 0.25
Christodoulou et al. 1995, f = form factor

13. STABLE UNSTABLE Probability of instability, lognormal distibution
Max. halo spin parameter for instability, as function of gas infall fraction
STABLE
Mestel
exponential
rigid
UNSTABLE

14. Global ang. mom. transport (“Bars within Bars”) :
M yr-1
Mass distribution isothermal,
Accumulated mass dominates for
BWB fails at ?

15. Local ang. mom. transport ( ) :
M yr-1
viscosity parameter (~1: Gammie 2001)
If T const. or incr. inwards, likely to reach center
FRAGMENTATION UNLIKELY TO STOP INFALL

16. TEMP./METALLICITY 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
FAVORS DIRECT BH FORMATION
FAVORS POP III STAR FORMATION

17. 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

18. RAPID GROWTH OF A PREGALACTIC BH
+ FORMATION OF THE SEED?
“QUASISTAR”
ACCUMULATED GAS
Pregalactic halo
Could seed BH grow from ~10 to >105 MSol at ?
(Begelman, Volonteri & Rees 06)

19. YOU’VE GOT TO BE KIDDING
WHAT IS A “QUASISTAR”?
Self-gravitating structure laid down by infall
Radiation-dominated, rotation crucial
Pre-BH:
Entropy small near center, increases with r
Very different from the supermassive stars postulated by Hoyle and Fowler
YOU’VE GOT TO BE KIDDING

20. WHAT IS A “QUASISTAR”? Self-gravitating structure laid down by infall
THAT’S BETTER
Self-gravitating structure laid down by infall
Radiation-dominated, rotation crucial
Pre-BH:
Entropy small near center, increases with r
Very different from the supermassive stars postulated by Hoyle and Fowler
Post-BH:
“Nuclear” energy source is BH accretion
Expands and becomes fully convective
Like radiation-dominated, metal-free red giant

21. QUASISTAR STRUCTURE : PRE-BH
Mass m* (M) increases with time M yr-1
Core with
Envelope
Entropy increases outward – convectively stable
Rotation increases binding energy
Outer radius constant
Core radius shrinks
Nuclear burning inadequate to unbind star
Core mass ~ 10 M constant
When core temp.
rapid cooling by thermal neutrinos

22. + CORE COLLAPSE AND FORMATION OF ~10-20 M SEED BH
SUBSEQUENT ACCRETION AT EDDINGTON LIMIT FOR QUASISTAR MASS

23. QUASISTAR STRUCTURE : POST-BH
BH accretes adiabatically from quasistar interior
Adjusts so energy liberated
Radiation-supported convective envelope (w/rotation)
Central temp drops to ~ 106 K
Radius expands to ~ 100 AU
Convection becomes inefficient well inside photosphere, where , but photosphere temp. drops as BH grows
Teff < 5000 K opacity crisis

24. OPACITY CRISIS Pop III opacity plummets below T~5000 K
Higher temp than for solar abundances

25. Mayer & Duschl 2005
Metal-free opacities

26. Metal-free opacities Mayer & Duschl 2005
Plausible range of photosphere densities
Analogous to Hayashi track, but match to radiation- dominated convective envelope

27. Mayer & Duschl 2005
Est. min. temp.
If Tphot drops below minimum (~5000 K), flux inside quasistar exceeds Eddington limit, dispersing it.

28. OPACITY CRISIS Pop III opacity plummets below T~5000 K
Higher temp than for solar abundances
If Tphot < 5000 K:
Photosphere migrates inward
Outer layers collapse (κ lower so flux sub-Eddington)
Core density increases higher
Super-Eddington flux in quasistar mass loss
Self-grav., so rotation can’t take up slack (unstable)
Unlike red giant, radn. pressure dominance + BH accretion physics may not permit static solution
Outcome unclear: Likely mass loss exceeds infall, quasistar eventually disperses

29. OPACITY CRISIS Pop III opacity plummets below T~5000 K
Higher temp than for solar abundances
Convection is relatively inefficient
Transition to radiative envelope at T~55,000 K ~ 10 Tphot
κ ~ κes at transition, but much lower at photosphere
If Tphot < Tmin , flux exceeds Eddington limit at transition quasistar disperses
Connect BH accretion physics to quasistar structure, predict Tphot(mBH, m*)

30. CONNECTION TO BH ACCRETION
Once limiting temperature is reached,
… dispersal is inevitable (and accelerates)

31. QUASISTAR MODELS WITH “TOY” OPACITY
Begelman, Rossi & Armitage 2007

32. QUASISTAR MODELS WITH “TOY” OPACITY
Begelman, Rossi & Armitage 2007

33. GROWING THE BLACK HOLE Eddington-limited growth:
Ignoring opacity crisis: M yr-1
Super-Eddington growth to ~107 M in yr
Onset of opacity crisis: Teff ~ 5000 K when
Estimates sensitive to:
Value of Tmin
Details of BH accretion
Energy loss details: rotational funnel, photon bubbles….

34. CAN QUASISTARS BE DETECTED?

35. DETECTING A QUASISTAR Most time spent as ~5000 K blackbody
Radiates at Eddington limit for 105m5 M
Max flux ~

36. JWST
z=6

37. JWST
z=6
z=20
z=10
PEAK OF BLACKBODY

38. DETECTING A QUASISTAR Most time spent as ~5000 K blackbody
Radiates at Eddington limit for 105m5 M
Max flux ~
Better to 3.5µm, on Wien tail
Corona/mass loss hard tail, easier detection

39. JWST
z=6
z=20
z=10
WIEN TAIL –
MASS LOSS MAY IMPROVE FURTHER

41. HOW COMMON ARE QUASISTARS?1
Nseeds (Mpc-3)
100 per L* galaxy
1 per L* galaxy
Cumulative comoving no. density of seeds
…but their lifetimes are short

42. COMOVING DENSITY OF QUASISTARS
No enrichment
L* galaxies
Lifetime = 106 yr
Some
enrichment
Metal enrichment model from Scannapieco et al. 2003
Heavy
enrichment

43. COMOVING DENSITY OF QUASISTARS
All 104 K haloes
100 per L* galaxy
Lifetime = 106 yr
104 K haloes with λ<0.02
1 per L* galaxy
Metal enrichment model from Scannapieco et al. 2003

45. DENSITY ON SKY 10-3 seeds Mpc-3 (1/L* gal.) 103.5 QS deg.-2
JWST FOV ~ 4.8 arcmin2
~ 1 per random field
Could be ~10-100x more common
How to distinguish from other objects?
Colors: ~pure blackbody (not dust reddened)
Observe on Wien tail
No lines (distinguish from T dwarfs)
Unresolved (distinguish from nearby starbursts)
Clustering (like 104 K haloes)

46. QUASISTAR DENSITY ON SKY
10/JWST field
1/JWST field
Lifetime = 106 yr

47. 100 per JWST field
10 per JWST field

48. WHAT HAPPENS NEXT?
If super-Edd. phase extends beyond opacity crisis, BH seeds could be as massive as 106 M
Worst case: super-Edd. phase ends at ~103 M
10 tSalpeter between z=10 and z= growth by (only) 20,000
BUT
Exceeding LEdd by factor squares growth factor!
Mergers can account for factor of growth

49. CONCLUSIONS I
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
BH seed can form in situ from the infalling envelope itself (aided by ν cooling) or can be captured Pop III remnant

50. CONCLUSIONS II
BH seeds grow inside a “quasistar” powered by BH accretion, with a radiation pressure-supported convective envelope
Min. Teff of quasistar is ~5000 K, lifetime is > 106 yr
Quasistars could be common and may be detectable by JWST