Massive Black Hole Growth and Formation

1

• Massive Black Hole Growth and Formation
• P.Coppi, Yale
• The Problem --
• Observational Constraints
• Clues
• Solutions?
• Pop. III Seeds
• Insights From Present-Day
• Star Formation
• Gas-Rich Mergers
• 3. Future Prospects Questions

Fan et al. 2003
2
HST QSO hosts
Bahcall et al. 2000
3
Timescale Problem
Need to pack a lot of gas into small region FAST!
4
Soltan 1982-type argument/problem
5
Observational Debates Clues Rare
long-lived AGN vs. many short-lived AGN?
Seems to be tilting decisively towards
6
IR Detection of AGN?
?
Cutri et al. 2001 Smith et al. 2001
Ready for SIRTF!
7
Where are the SMBH binaries?
3C 75 Merger Starting?
Owen, VLA
8
Smoking Gun?
NGC 326
Ekers Merrit, 2002
9
From the Dark Ages to the Cosmic Renaissance

• First Stars Transition from Simplicity to
  Complexity

10
Region of Primordial Star Formation

• Gravitational Evolution of DM
• Gas Microphysic
• - Can gas sufficiently cool?
• - tcool lt tff (Rees-Ostriker)

• Collapse of First Luminous Objects expected

• at zcoll 20 30
• with total mass M 106 Mo

11
How massive were the First Stars?
M 106 Mo
normal IMF
Top-heavy IMF
Cluster of Stars
Massive Black Hole
Previous estimates 1 Mo lt MPopIII lt 106 Mo
12
The Physics of Population III

• Simplified physics
• No magnetic fields yet (?)
• No metals no dust
• Initial conditions given by CDM
• Well-posed problem
• Problem
• How to cool primordial gas?
• No metals different cooling
• Below 104 K, main coolant is H2
• H2 chemistry
• Cooling sensitive to H2 abundance
• H2 formed in non-equilibrium
• Have to solve coupled set of rate
  equations

Metals
Atomic cooling
H_2 cooling
Tvir for Pop III
13
Simulating the Formation of the First Stars
(Bromm, Coppi, Larson and Bromm Hernquist)

• Use TREESPH / Gadget (both DM and gas)
• Radiative cooling of primordial gas
• Non-equilibrium chemistry
• Initial conditions ?CDM
• Modifications to SPH
• - sink particles
• - particle splitting

14
Cosmological Initial Conditions

• Consider situation at z 20

Gas density
Primordial Object
7 kpc
15
The First Star-Forming Region
M 106 Mo
1 kpc
7 kpc
16
Formation of a Population III Star
Mhalo 106 Mo
Mclump 103 Mo
25 pc
1 kpc
(see also Bromm, Coppi, Larson 1999, 2002)
17
A Physical Explanation

• Gravitational instability (Jeans 1902)
• Jeans mass
• MJT1.5 n-0.5

• Thermodynamics of primordial gas

T vs. n
MJ vs. n

• Two characteristic numbers in
• microphysics of H2 cooling
• - Tmin 200 K
• - ncrit 103 - 104 cm-3 (NLTE LTE)
• Corresponding Jeans mass MJ 103 Mo

18
A Tale of Two Timescales

• Consider the cooling and freefall times

Timescale vs. n
tff tcool

• Gas particles loiter at n 103 104 cm-3
• - tcool tff
• - Quasi-hydrostatic phase
• Runaway collapse occurs
• - s.t. tcool tff

19
The Crucial Role of Accretion

• Final mass depends on accretion from dust-free
• Envelope
• Development of core-envelope structure
• - Omukai Nishi 1998 , Ripamonti et al.
  2002
• Mcore 10-3 Mo very similar to Pop. I
• Accretion onto core very different!
• dM/dtacc MJ / tff T3/2 (Pop I T 10 K, Pop
  III T 300 K)
• Can the accretion be shut off in the absence of
  dust?

20
Protostellar Collapse (Bromm Loeb 2003,
astro-ph/0301406)

• Simulate further fate of the clump

25 pc
0.5 pc
21
The Crucial Role of Accretion
M vs. time
dM/dt vs. time
22
The Death of the First Stars
(Heger et al. 2002)
Pop I
Z
PISN
Pop III
Initial Stellar Mass
23
The First Supernova Explosions
(with N. Yoshida L. Hernquist)
M 106 Mo
1 kpc
7 kpc
24
HII Regions around the First Stars
1 kpc
25
The First Supernova-Explosion
Gas density

• ESN1053ergs

• Complete
• Disruption
• (PISN)

1 kpc
26
Paradise Lost The Transition to Population II
(Bromm, Ferrara, Coppi,
Larson 2001, MNRAS, 328, 969)

• Add trace amount of metals
• Limiting case of no H2
• Heating by photoelectric
• effect on dust grains

Cooling Rate vs. T
Consider two identical (other than Z) simulations
!
27
Effect of Metallicity
Z 10-4 Zo
Z 10-3 Zo

• Insufficient cooling

• Vigorous fragmentation

Critical metallicity Zcrit 5 x 10-4 Zo
28
En Route to a Supermassive Black Hole?

• Consider gas distribution in central 100 pc

Low-spin
High-spin
Single object M 106 Mo
Binary M1,2 106 M0
29
Tsuribe 2000
30
Simulation of idealized gas-rich merger A. Escala
Dynamical friction phase
31
Binary-dominated (self-similar?) phase
32
Fast merger?
33
Summary (questions) Merger vs. accretion? Both?
? Primordial (Pop. III) seeds plausible, very
high z mini-AGN/mergers/GRBs? Where are the
binaries? (maybe binaries dont accrete
efficiently?) Where are the IMBH? Do intense
radiation fields lead to top-heavy IMFs? More
interesting observations to come better
X-ray follow-ups, SIRTF, LISA Theorists hard at
work to catch up (feedback is the main problem)
34
The First Supernova-Explosion
Metal Distribution
1 kpc
35
Thermodynamics and Structure
Phase Distribution
T vs. log n
36
Dense-shell Formation
Timescale vs Radius
Inverse Compton cooling
tff
tshock
tcool
37
The First Supernova-Explosion
Gas density

• ESN1053ergs

• ESN1051ergs

1 kpc

• Complete
• Disruption
• (PISN)

38
Nucleosynthetic Evidence (Qian Wasserburg
2002)
Heavy r-process abund. vs. Fe/H

• Signature of VMS enrichment at Fe/H lt -3
• Normal (Type II) SNe at higher Fe/H

Zcrit
39
Cosmic Star Formation History (Mackey, Bromm
Hernquist 2003)
Comoving SFR vs. redshift

• 2 modes of SF
• - Pop III VMS
• - Pop I / II normal stars
• Pop III SF possible
• in halos with
• - Tvir lt 104 K molecular cooling
• - Tvir gt 104 K atomic H cooling

Pop III
Pop I / II
(Springel Hernquist 2003)
40
Cosmic Star Formation History (Mackey, Bromm
Hernquist 2003)
Comoving SFR vs. redshift

• Dominant Pop III SF
• expected in halos with
• Tvir gt 104K atomic H cooling
• Strong negative feedback
• suppresses SF in mini-halos
• (radiative and mechanical)

Pop III
41
The Pop III Pop II Transition
(Mackey, Bromm Hernquist 2003)
Metallicity SFR vs. redshift
Zcrit
50
5
ztran 15 - 20
42
Relic of the Dawn of Time

• HE0107-5240 Fe/H - 5.3 (Christlieb et al.
  2002)

• What does this star tell us about Population III
  ?

43
Metal Poor Halo Stars and the First Stars (with
Schneider, Ferrara, Salvaterra, Omukai 2003,
Nature in press)

• Abundance pattern
• - core-collapse SN
• - PISN
• Break degeneracy
• - r-process elements
• Z lt Zcrit ?
• - role of dust
• - shock-compression
• - statistics

44
Formation of the First Quasars (Bromm Loeb
2003, astro-ph/0212400)

• Seed BH by direct collapse of primordial gas
  cloud

(Loeb Rasio 1994, ApJ, 432, 52)
Stars Gas

• Problem
• - Gas cooling
• - Fragmentation
• - Star Formation
• - Negative Feedback (SNe)
• No compact central object!

Mass 109 Mo, R 1 kpc zvir 5, no DM
45
First Dwarf Galaxies as Sites of BH Formation
T vs. log n

• 2 sigma peak
• M 108 M0, zvir 10
• Tvir 104 K
• Cooling possible due to
• atomic H

- Photo-dissociation of H2 H2 h nu
2 H - Lyman Werner photons h nu
11.2 13.6 eV

• Suppress star formation

Tvir 104 K
46
Gamma-Ray Bursts as Probes of the First Stars

• GRB progenitors massive stars
• GRBs expected to trace cosmic SFH
• Swift mission
• - Launch in 2003
• - Sensitivity
• GRBs from z gt 15

47
Expected Redshift Distribution of GRBs
( Bromm Loeb 2002, ApJ, 575, 111 )
SF History
GRB Redshift Distribution
(Cf. Barkana Loeb 2000, ApJ, 539, 20)

• Fraction of all burst from z gt 5 50
• Fraction of GRBs detected by Swift from z gt 5
  25

48
Summary

• Primordial gas typically attains
• - T 200 300 K
• - n 103 104 cm-3
• Corresponding Jeans mass MJ 10 3 Mo
• Pop III SF might have favored very massive
  stars
• Transition to Pop II driven by presence of
  metals
• (ztrans 15 20)
• PISNe completely disrupt mini-halos and enriches
  surroundings
• Metal-poor halo stars as probes of the first
  stars

49
Perspectives
Further fate of clumps - Feedback of
protostar on its envelope - Inclusion of
opacity effects (radiative transfer) The
Second Generation of Stars SN feedback and
metal enrichment from the first stars How does
a VMO evolve and die? Observability (lensing?)
and statistics of high-z SNe
50
132 node Beowulf cluster (AMD Athlon)
51
The Mass of a Population III Star

• Central core in free-fall M 100 Mo
• Extended envelope with isothermal density
  profile
• First stars were predominantly very
  massive

52
Implications of a Heavy IMF For the First Stars
(Bromm, Kudritzki, Loeb 2001, ApJ,
552, 464)

• Consider 100 Mo lt M lt 1000 Mo (VMO)
• Structure determined by
• - Radiation pressure, Luminosity close to
  EDDINGTON limit

log L vs. log Teff

• For Pop III
• Teff 110,000 K
• lambda peak 250 A
• (close to He II ionization edge)

53
How Do VMOs Evolve ?
log L vs. log Teff

• Nuclear burning up
• He ignition
• Estimated lifetime
• 3 x 106 yr
• Crucial uncertainty
• Mass loss ???

54
Spectral Signature

• Strong NLTE effects
• Close to black-body form
• Lines of H I and He II

Flux vs. Wavelength
55
A Generic Spectrum
L nu / M vs. lambda

• Spectra very similar for M gt 300 Mo
• Predict composite spectrum
• almost independent of IMF

• Ionizing photon production
• Rare 3 sigma peaks may suffice to reionize the
  Universe

56
Probing the Primordial IMF with NGST

• Observed spectrum Heavy IMF vs. Salpeter IMF

Observed flux vs. Wavelength
- Salpeter case from Tumlinson Shull 2000

• Observed spectrum from cluster with heavy IMF is
  significantly bluer

57
Why Study Population III?

• The Quest for our Origins
• Importance for Cosmological Structure Formation
• Reheat / Reionize the Universe
• Feedback effects on IGM
• Initial enrichment with metals
• Pure H/He out of BBNS
• Need stars to synthesize heavy
  elements
• Pop III remnants
• Baryonic DM (?)
• Upcoming Observations
• CMB anisotropy probes (WMAP / Planck)
• Study imprint of first stars
• IR missions (SIRTF/ JWST)
• Direct imaging