massive black hole growth and formation: implications for lisa · massive black hole growth and...
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Massive Black Hole Growth and Formation:Implications for LISA
1. Supermassive Black Holes:When, Where, and How?
Theoretical IssuesObservational Constraints
& Clues
2. Does a Galaxy Merger Imply a Black Hole Merger?
Where Are the Binaries? Gas-Rich vs. Gas-Poor Mergers
3. What About the LMBH?Do They Exist? Pop. III Seeds Fan et al. 2003
P.Coppi, Yale
The existence of massiveblack holes is not necessarily so surprising.Many roads lead to a massive black hole?(Gravity is one way.)
Rees 1984
2
6Salpeter 0.1
9Hubble
vs.4 /
exponential growth on timescale
t 45 10 yr4
t ( 6) 10 yr, i.e., marginally sufficient number of
acc BH
Edd BH p T
T
p
L M cL GM m
cGm
z
επ σ
εσ επ
=
=
→
= ≈
≤
&
6 8acc
growth e-foldings possible (even for 100 M seed)
Problem worse if t / ( / ) 10 10 yrAGN Gal oN N c H −
Timescale Problem:
Need to pack a lot of gas into small region FAST!
Formation of the First Quasars
• Seed BH by direct collapse of primordial gas cloud
Mass ~ 109 Mo, R ~ 1 kpczvir = 5, no DM
Stars Gas (Loeb & Rasio 1994, ApJ, 432, 52)
• Problem:
- Gas cooling- Fragmentation
No compact central object!
Neglected- Star Formation- Negative Feedback (SNe)
How to make life easier?
Give up Eddington limit? Not so hard… accreting compact objects in our galaxy seem to do it!
Remember Eddington limit only applies to isotropic configurations, while gas flows in strongradiation fields are not. If really throw a lot of gas ontohole, can trap radiation and advect it into hole (e.g., Begelman 1978)
Pre-existing Massive Seeds!
Are they big (106 solar masses) or small (10-100solar masses)?
When do they appear and how rare are they?Big impact on LISA event rate!
Bahcall et al. 2000
HST QSO hosts
A “boring” object in the sky: the nearby elliptical galaxy M87
Optical
Radio
Soltan 1982-type argument/problem:
5 1 3
6 1 3lg
lg /
1.4 10 ( / 0.01)
.
1.1 10 ( / 0.002)( / 0.002 )
acc B
BHrelic BH Bu e
Bu e
f M Mpc
vsMh h M MpcM σ
ρ ε
ρ
− −
− −
= ×
= × < > Ω
accretion irrelevant, mergers key? most of accretion activity missed, i.e, "dark" (dust obscuration, low radiative eff
/ 1?
iciency
acc BHρ ρ ⇒
accretion solns: super-Eddington photon-trapping, ADAF, etc.)
(e.g., Natarajan 1999 review)
Gilli 2003 review – astro-ph/0303115
The X-Ray Background (mostly AGN, hard X-rays clean BH signal)
Urry & Padovani 1995
The “Unified” AGNModel:
Type I Type 2
Orientation Effect?
Type I
“Type II”
+
The standard ingredientsfor an XRB model(e.g., Comastri et al. 1995,Gilli et al. 2002)
Deep ROSAT (one week exposure) of Lockman Hole Region
1000-2000+ sources per square degree!
[Chandra spacecraft can do this in half a day!]An image in only the 0.3-2.0 keV energy band
CDF-N/GOODS, 2Msec(!) Chandra
CDF-S
The acid test: what happens when you start adding hard X-rays?
Aside: Chandra < 1” angular resolution absolutelycritical! At R=27+ (>40% faint Chandra sources),optical source density is huge …[counterpart confusion serious problem for ROSAT,and even XMM]
Real HST GEMS data, w/real Chandra (1.5”) + simulated XMM (8”) error circles superimposed.
Success?!
NO!
Hasinger 2003
Hasinger et al. 2003 version N.B. cosmic variance!
Broad LineNarrow Line
?Unknown
Morenarrow linelow-powerobjectsat lower z?
Berger et al. 2003
Wilkes et al. 2002
If select quasars by non-standardtechnique, indeedfind “weird” objects!
2MASS Red/NIRQuasar Survey
(very bright,nearby objects;analog of Hellas2XMM)
Some showbroad optical emissionlines but absorbedX-rays??
Standard, old result
Heckman (+ SDSS) 2003
Sample of 56,000emission-linegalaxies!
starbursts
?composite
Further complications… confusion w/starburst
Cutri et al. 2001; Smith et al. 2001
?
IR Detection of AGN?
Ready for SIRTF!
In general, nice ROSATera correlations kaput …
(mass-velocity dispersion)
(mass-bulge luminosity dispersion)
2x disagreement?
vs. [Yu & Tremaine 2002]
Observational Debates & Clues
Rare long-lived AGN vs. many short-lived AGN?Seems to be tilting decisively towards
relation, ( many relic SMBH)X-ray/2MASS counts ( many active AGN missed optically)No more Soltan/ problem?
M
M
σ
σ
−⇒
⇒−
Also, relation BH and galaxy know about each other!? Galaxy & BH formation same process? (Once correct for obscuration, redshift evolution s
M σ− ⇒
imilar?)
Mergers/gas are clearly important in at least AGN phase.
Owen, VLA
3C 75: Merger Starting?
Where are the SMBH binaries?
“Smoking Gun?”
Ekers &Merrit, 2002
NGC 326
NGC 6240:current best case foran eventual merger?
Simulation of idealized gas-rich merger…
Dynamicalfriction phase
A. Escala 2003
What happenswhen a binaryforms?
Drag continues!
(If there’senough gas…)
Merger happens very fast!
Bender and Pollack 2003
Black holesin globular clusters?
One of best studied cases : M15
a 2000 solar mass black hole?
Guhathakurta et al. 1996
Gebhardt et al. 2000
?
ULXsandIMBHs
M82Fabbiano et al. 2001, CXO
How massive were the First Stars?
Previous estimates: 1 Mo < MPopIII < 106 Mo
M ~ 106 Mo
Massive Black Hole Cluster of Stars
normal IMF Top-heavy IMF
Atomic cooling
H_2 cooling
The Physics of Population III
• Simplified physicsNo magnetic fields yet (?)No metals no dustInitial conditions given by CDM
Well-posed problem• Problem:
How to cool primordial gas?No metals different coolingBelow 104 K, main coolant is H2
• H2 chemistryCooling sensitive to H2 abundanceH2 formed in non-equilibrium
Have to solve coupled set of rate equations
Metals
Tvir for Pop III
Cosmological Initial Conditions• Consider situation at z = 20
Gas density
~ 7 kpcPrimordial Object
The First Star-Forming Region
~ 7 kpc1 kpc
M ~ 106 Mo
A Physical Explanation:
• Gravitational instability (Jeans 1902)• Jeans mass:MJ~T1.5 n-0.5
T vs. n MJ vs. n
•Thermodynamics of primordial gas
•Two characteristic numbers in microphysics of H2 cooling:
- Tmin ~ 200 K- ncrit ~ 103 - 104 cm-3 (NLTE LTE)
• Corresponding Jeans mass: MJ ~ 103 Mo
The Crucial Role of Accretion
• Final mass depends on accretion from dust-freeEnvelope
• 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?
The Death of the First Stars:(Heger et al. 2002)
Initial Stellar Mass
Z
Pop III
Pop I
PISN
What happens to pop IIIremnant BH?Madau et al. 2003?
First Dwarf Galaxies as Sites of BH Formation
• 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
T vs. log n
Tvir ~ 104 K
• Suppress star formation:
(Bromm & Loeb 2003)
En Route to a Supermassive Black Hole?
• Consider gas distribution in central 100 pc
Single object: M ~ 106 Mo
Low-spin High-spin
Binary: M1,2 ~ 106 M0
Summary:
SMBH growth must be a rapid and relatively robust process. Can happen very early on. Probably intimately tied to galaxy merger induced activity,especially nuclear star formation (M-σ relation!).
Observations of SMBH improving rapidly. Field in state of flux. Chandra + SIRTF especially powerful, overcome obscuration problem to uncover true AGN and star formation activity.
SBMH growth by merger vs. accretion? Both? Today, looks like accretion may be dominant mode.
SMBH growth greatly facilitated by pre-existing massive “seeds.” Nature of number of seeds is major uncertainty in expected LISA event rate.
Primordial (Pop. III) seeds appear plausible => very high z mini-AGN, WMAP reionization? Mergers and GRBs? High overall LISA rate? Especially if M-σ relation holds for early AGN, LISA powerful probe of early structure formation, at z > 10!?
Would be reassuring to actually find some MBH binaries before LISA. Where are they? Maybe binaries don’t accrete efficiently? NGC 6240 currently best and perhaps cautionary example. Binary BH merge quickly and are obscured? If so, EM counterpart to LISA signal may be difficult to find? Angular resolution key to finding correct counterpart.
Would also be nice to find IMBH/LMBH. Evidence scant right now. IMHO, most ULXs are NOT IMBH but beamed/super-Eddington stellar mass objects (e.g., GRS 1915 in our galaxy). However, a few ULXs are best explained as massive objects and there are a couple known AGN with
Large characteristic Jeans mass for fragmentation might actually occur today, e.g., in galactic nuclei. Strong ionizing radiation field (e.g., from AGN) wipes out metal coolants, heats gas? Top heavy IMF? Most massive stars in our galaxy near galactic center. More massive remnants + dissipative central gas => good for LISA!
Effects of BH spin seems to be major LISA signal uncertainty. If MBH grow by accretion, easy to get maximally rotating hole. Don’t ignore!?
510 .M M≤
Metal abundance higher than solar, everythingHappens fast
Abandon eddington limit
Seed
Small or not? Blob vs. hierarchical formation?
Tightness of M-sigma?Easy to understand scalingWhy the constant, ie., why scatter so small?
Seeds!!!
Lesson from present day star formation
Bender “LMBH”
Henry 1999
The Diffuse Extragalactic Background
EnergeticParticles!
From the Dark Ages to the Cosmic Renaissance
• First Stars Transition from Simplicity to Complexity
Berger et al. 2003
Cooling Rate vs. T
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 photoelectriceffect on dust grains
Consider two identical (other than Z) simulations !
Effect of Metallicity:
Z = 10-4 Zo Z = 10-3 Zo
• Insufficient cooling • Vigorous fragmentation
Critical metallicity: Zcrit ~ 5 x 10-4 Zo
The First Supernova-ExplosionGas density
~ 1 kpc
• ESN~1053ergs
• Complete Disruption(PISN)
Barger et al.2003(CDF-N)
Extra objectsat wrong redshift(s)!
old objects
Region of Primordial Star Formation
• Gravitational Evolution of DM
• Gas Microphysic:
- Can gas sufficiently cool?- tcool < tff (Rees-Ostriker)
• Collapse of First Luminous Objects expected:
- at: zcoll = 20 – 30
- with total mass: M ~ 106 Mo
A Tale of Two Timescales
• Gas particles loiter at: n ~ 103 – 104 cm-3
- tcool ~ tff- Quasi-hydrostatic phase
• Runaway collapse occurs- s.t. tcool ~ tff
• Consider the cooling and freefall times:Timescale vs. n
tff
tcool
The First Supernova Explosions(with N. Yoshida & L. Hernquist)
~ 7 kpc1 kpc
M ~ 106 Mo
HII Regions around the First Stars
1 kpc
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: ΛCDM
• Modifications to SPH:- sink particles
- particle splitting
The First Supernova-ExplosionMetal Distribution
~ 1 kpc
Thermodynamics and Structure
T vs. log n Phase Distribution
Dense-shell Formation
Timescale vs Radius
tcool
tff
Inverse Compton cooling
tshock
The First Supernova-ExplosionGas density
~ 1 kpc
• ESN~1053ergs
• Complete Disruption(PISN)
• ESN~1051ergs
Nucleosynthetic Evidence:(Qian & Wasserburg 2002)
• Signature of VMS enrichment at [Fe/H] < -3
• Normal (Type II) SNe at higher [Fe/H]
Heavy r-process abund. vs. [Fe/H]
Zcrit
Cosmic Star Formation History(Mackey, Bromm & Hernquist 2003)
• 2 modes of SF:- Pop III VMS- Pop I / II normal stars
• Pop III SF possible in halos with:- Tvir < 104 K molecular cooling
- Tvir > 104 K atomic H cooling
Comoving SFR vs. redshift
Pop I / II Pop III(Springel & Hernquist 2003)
Cosmic Star Formation History(Mackey, Bromm & Hernquist 2003)
• Dominant Pop III SFexpected in halos with:Tvir > 104K atomic H cooling
• Strong negative feedbacksuppresses SF in mini-halos
(radiative and mechanical)
Comoving SFR vs. redshift
Pop III
The Pop III Pop II Transition(Mackey, Bromm & Hernquist 2003)
Metallicity SFR vs. redshift
ztran~ 15 - 20
Zcrit
50%
5%
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 ?
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 < Zcrit ?- role of dust- shock-compression- statistics
First Dwarf Galaxies as Sites of BH Formation
• 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
T vs. log n
Tvir ~ 104 K
• Suppress star formation:
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 > 15
Expected Redshift Distribution of GRBs:( Bromm & Loeb 2002, ApJ, 575, 111 )
(Cf. Barkana & Loeb 2000, ApJ, 539, 20)
SF History GRB Redshift Distribution
• Fraction of all burst from z > 5: ~ 50%• Fraction of GRBs detected by Swift from z > 5: ~ 25%
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
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
132 node Beowulf cluster (AMD Athlon)
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
Implications of a Heavy IMF For the First Stars(Bromm, Kudritzki, Loeb 2001, ApJ, 552, 464)
• Consider: 100 Mo < M < 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)
How Do VMOs Evolve ?
log L vs. log Teff • Nuclear burning up He ignition• Estimated lifetime:
3 x 106 yr
• Crucial uncertainty:Mass loss ???
Spectral SignatureStrong NLTE effects
• Close to black-body form
• Lines of H I and He II
Flux vs. Wavelength
A Generic SpectrumL nu / M vs. lambda
• Spectra very similar for M > 300 Mo
• Predict composite spectrum
almost independent of IMF
• Ionizing photon production
• Rare 3 sigma peaks may suffice to reionize the Universe
Probing the Primordial IMF with NGST• Observed spectrum: Heavy IMF vs. Salpeter IMF
Observed flux vs. Wavelength
• Observed spectrum from cluster with heavy IMF is significantly bluer
- Salpeter case fromTumlinson & Shull 2000
Why Study Population III?• The Quest for our Origins• Importance for Cosmological Structure Formation
Reheat / Reionize the UniverseFeedback effects on IGM
Initial enrichment with metalsPure H/He out of BBNSNeed stars to synthesize heavy elements
Pop III remnantsBaryonic DM (?)
• Upcoming ObservationsCMB anisotropy probes (WMAP / Planck)
Study imprint of first starsIR missions (SIRTF/ JWST)
Direct imaging
The Crucial Role of AccretiondM/dt vs. time M vs. time
55.0
dd −∝ ttM 45.0tM ∝∗
Gilli 2003 review (astro-ph/0303115)
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