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Transcript of Discuss topics in sequence with the question at the top of each slide.
Discuss topics in sequence with the question at the top of each slide.
Astrophysical Black Holes: Astrophysical Black Holes: Key QuestionsKey Questions
Avi Loeb
Harvard University
Fourth Sackler conference, May 15-18, 2006
Key questionsKey questions• Is general relativity the correct description of strong gravity?Is general relativity the correct description of strong gravity?
Do black holes exist?Are they described by the Kerr metric (with the predicted properties of the event horizon, innermost stable circular orbit, photon orbit, etc.)?
• What is the spin and mass distribution of astrophysical black holes? What is the spin and mass distribution of astrophysical black holes? Why?Why?
• What is the history of black hole formation and evolution? What is the history of black hole formation and evolution? How did the first black holes form? How did the first black holes form? Was growth dominated by accretion of gas, consumption of stars or mergers? Do Was growth dominated by accretion of gas, consumption of stars or mergers? Do binaries coalesce? What is the impact of gravitational-wave recoil?binaries coalesce? What is the impact of gravitational-wave recoil?
• How do black holes accrete gas? How do black holes accrete gas? What are the geometry and radiative efficiency of the accretion flow as a function of What are the geometry and radiative efficiency of the accretion flow as a function of the accretion rate? Which fraction of the infalling mass is expelled in outflows?the accretion rate? Which fraction of the infalling mass is expelled in outflows?
• In what form do black holes release accretion energy? In what form do black holes release accretion energy? What is What is the relative fraction of radiation, magnetically-dominated outflows, relativistic the relative fraction of radiation, magnetically-dominated outflows, relativistic particles, non-relativistic winds, neutrinos, gravitational waves?How are relativistic particles, non-relativistic winds, neutrinos, gravitational waves?How are relativistic jets produced? Are they made of e+e- or baryons?jets produced? Are they made of e+e- or baryons?
• How do nuclear black holes influence the evolution of their host How do nuclear black holes influence the evolution of their host galaxies, X-ray clusters, or the larger-scale intergalactic medium?galaxies, X-ray clusters, or the larger-scale intergalactic medium? What is the origin of the correlations between What is the origin of the correlations between black hole mass and spheroid properties?black hole mass and spheroid properties? What sets the maximum mass of galaxies?What sets the maximum mass of galaxies?
The Black Hole in the Galactic Center: SgrA*
VLT with Adaptive Optics
•“3-color”: 1.5 - 3 um
• 8.2 m VLT telescope
• CONICA (IR camera)
• NAOS (adaptive optics)
• 60 mas resolution
Simultaneous fit of orbits implies:
1. BH mass:
2. BH proper motion: < 0.8+-0.7 mas/yr
(4æ0:3) â (d=8kpc)3 â 106M ì
Ghez et al. 2003
SO-16 closest approach at 90 AU
Genzel et al 2003
Water Masers: NGC 4258
Moran, Greenhill, & Herrnstein (2000)
Keplerian Velocity Profile
Miyoshi et al. 1995
Broderick & Loeb 2005
Is general relativity a valid description of strong gravity?Is general relativity a valid description of strong gravity?
*Infrared variability of flux (Genzel et al.) and polarization (Eckart et al.) of SgrA*: hot spots.
*Innermost Stable Circular Orbit: radius of 30 (10) micro-arcsecond and orbital time of 30 (8) minutes for a non-rotating (maximally-rotating) black hole at the Galactic center
*A hot spot would result in infrared centroid motion (PRIMA-VLT) and could be imaged by a Very Large Baseline Array of (existing) sub-millimeter observatories. Targets:SgrA* and M87
What is the spin distribution of What is the spin distribution of astrophysical black holes?astrophysical black holes?
Volonteri, Madau, Quataert, & Rees (2005)
Contribution from Gas accretion dominates
over mergers
What is the history of black hole What is the history of black hole formation and evolution?formation and evolution?
The First Dark Matter Objects in the Universe
Smallest dark matter clumps: ~0.1 Jupiter mass
Loeb & Zaldarriaga, astro-ph/0504112
Diemand, Moore & Stadel astro-ph/0501589
Emergence of the First Star Clusters
molecular hydrogen
Yoshida et al. 2003
Cooling Rate of Primordial Gas
n=0.045 cm^-3
Atomic cooling
H_2 cooling
Virial Temperature of Halos
1-sigma 2-sigma
3-sigma
Atomic cooling
H_2 cooling
Massive Accretion by Pop-III Proto-StarsMassive Accretion by Pop-III Proto-Stars
23.5pc 0.5pc
Bromm & Loeb, New Astronomy, 2004; astro-ph/0312456
Resolving accretion flow down to ~0.03 pc
Formation of Massive Black Holes in the First Galaxies
Add Bromm
Low-spin systems: Eisenstein & Loeb 1995
Numerical simulations: Bromm & Loeb 2002
R < 1pc
M 1 ø 2:2â 106M ì
M 2 ø 3:1â 106M ì
õ = 0:05
H2 suppressed
Supermassive StarsSupermassive Stars
Teff ø 105K
L = L E / M
For a spherical (non-rotating) star:general-relativistic instability at
(Rc2GM)crit = 0:6295( M
M ì )1=2
Angular momentum mass shedding along equator
Collapse to a black hole is inevitable for M > 300M ì
High spin disks: Loeb & Rasio 93; Low-spin disks: Eisenstein & Loeb 95
S. Shapiro, et al. 2003
Growth of Supermassive Black HolesGrowth of Supermassive Black Holes
tE = M=Mç = 4â 107(L=L E)(ï=10%)years
L = ïMçc2
M / expf t=tEg
Why Are Quasars Short Lived?Why Are Quasars Short Lived?
Principle of Self Regulation: supermassive black holes grow until they release sufficient energy to unbind the gas that feeds them from their host galaxy
Because they are suicidal!
Implies a correlation between black hole mass and the depth of the gravitational potential well of its host galaxy
(M bh=M galaxy) < 10à 3(NQuasars=NGalaxies) < 10à 2 ;
Quasar Luminosity Function
Wyithe & Loeb astro-ph/0304156
Simple physical model:
*Each galaxy merger leads to a bright quasar phase during which the black hole grows to a mass and shines at the Eddington limit. The duration of this bright phase is dictated by the dynamical time of the host galactic disk (7% of the total energy release can unbind the disk on its dynamical time).
*Merger rate: based on the extended Press-Schechter model in a LCDM cosmology.
duty cycle ~10 Myr
M ï / v5c
Hydrodynamic Simulations of Quasar FeedbackHydrodynamic Simulations of Quasar Feedback
Springel, Hernquist, Di Matteo et al. 2005
Hydrodynamic Simulations of Quasar FeedbackHydrodynamic Simulations of Quasar Feedback
Mç = minfBondi à rate;Eddington à rategenergy à feedingà rate= 5%â 10%â Mçc2
(Springel, Di Matteo, (Springel, Di Matteo, & Hernquist 2004)& Hernquist 2004)
(Springel, Di Matteo, & Hernquist 2004)(Springel, Di Matteo, & Hernquist 2004)
How do black holes accrete gas?How do black holes accrete gas?
Stone et al. 2005
What is the accretion rate into SgrA*horizon?
MçB ø 10à 5M ì yrà 1
Bolometric luminosity: ø 1036erg=s
Mç ø 2â 10à 10M ì yrà 1(ï=0:1)à 1
Bondi rate:
Feeding SgrA* with Stellar Winds
Loeb, astro-ph/0311512
J < J max = ñ c4GM ï
ð ñEmission region:Emission region:
In what form do black holes In what form do black holes release accretion energy?release accretion energy?
• Radiation
• Non-relativistic wind
• Relativistic particles and magnetized jets
• Neutrinos
• Gravitational radiation
Injection of Positrons from AGN Jets
Furlanetto& Loeb 2002
AGN
e+e- jet
Spectrum of Positron Annihilation Line3-photon decay of Positronium does not smear line due to keV temperature of cluster electrons (direct annihilation more probable)
Line signal detectable with INTEGRAL (launched Oct. 2002) and EXIST (space station) for rich X-ray clusters out to 100 Mpc
More details: ApJ, 572, 796 (2002)
Black Hole Binaries due to Galaxy Mergers
X-ray Image of a binary black hole system in NGC 6240
Komossa et al. 2002
z=0.025
10kpc
Dynamics of black hole binaries
Chatterjee, Hernquist, & Loeb 2002
Figure1.ps
Typical binaries coalesce in less than 10 Gyr due to wandering
Numerical experiment:
400,000 stars
R
M=M ? = 0:25%
kick velocity from galaxies
Gravitational Wave Amplitude from a Black Hole Binary at z=1
Gravitational Radiation from Coalescence of Massive Black Hole Binaries
Wyithe & Loeb 2002
LISA
PULSARS
REDSHIFT FREQUENCY (Hz)
How do nuclear black holes influence the evolution How do nuclear black holes influence the evolution of their host galaxies, X-ray clusters, or the larger-of their host galaxies, X-ray clusters, or the larger-
scale intergalactic medium?scale intergalactic medium?
Fabian et al. 2003Kraft et al. 2005
• What is the dominant mechanism that mediates the energy transfer? acoustic waves, relaticistic particles and magnetic fields
• Is the growth of the stellar spheroid affected by this feedback?
McNamara et al. 2005 Forman et al. 2003
Correlation between black hole mass and velocity dispersion of host stellar system
Tremaine et al. 2002
ì = 4:02æ0:32;ë = 8:13æ0:06
ì = 4:02æ0:32;ë = 8:13æ0:06
ë = 8:22æ0:07
ì = 4:58æ0:52
Ferrarese 2002
log(M=M ì ) = ë + ì log(û?=200km=s)
Self-regulation of Supermassive Black Hole Growth
quasar
! 108M ì
M bh = 1:5 200km=sû
ð ñ5
Ltdyn ø 23M gasû2
dynamical time of galactic disk maxf Lg = L E / M bh
halo velocity dispersion
After translating û ! û? this relation matches the observed correlation in nearby galaxies (Tremaine et al. 2002; Ferarrese & Merritt 2002)
M à ûã
Silk &Rees 1998; Wyithe & Loeb 2003
M ?
M bh / f ?
û2
â (1+ z)3=2
Clustering Statistics of QuasarsClustering Statistics of Quasars
Wyithe & Loeb 2004; Wyithe & Loeb 2004; astro-ph/0403714astro-ph/0403714
Lines:Lines: correlation function of model with
L = L E
M bh / v5c
Data points:Data points:
2dF Quasar Survey (Boyle et al. 2000)
(SIS)
Data on Quasar Clustering/LF Implies:Data on Quasar Clustering/LF Implies:
M bh / v5c
M bh / M 5=3halo
• Local relation between galactic halo/black-hole + redshift evolution of quasar correlation length are consistent with
and not
• If mergers trigger quasar activity, then quasar lifetime scales with dynamical time of host galaxy
rather than the redshift-independent Salpeter-Eddington time for its growth / (1+ z)à 3=2
tE = 4â 107(ï=0:1)years
Wyithe & Loeb 2004; astro-ph/0403714Wyithe & Loeb 2004; astro-ph/0403714
Effects of Quasars on the Intergalactic Medium: Ionization and Magnetization
The Earliest Quasar Detected:The Earliest Quasar Detected: zz=6.4=6.4
Fan et al. 2002
Cosmic Hydrogen was significantly Neutral at z~6.3Cosmic Hydrogen was significantly Neutral at z~6.3
Wyithe & Loeb, Nature, 2004; astro-ph/0401188
Size of HII region depends on neutral fraction of IGM prior to quasar activity and quasar age
Ionization(Stromgren) sphere of quasar
line of sight
R(t)
Cosmic Background Radiation
Gamma-ray background
Quasars as Perturbers:Impact of Quasar Outflows on the IGM
Furlanetto & Loeb 2001
Intergalactic Medium (IGM)
Is the IGM fully magnetized just like the ISM?
jetBAL outflow
quasar
small-scale structure; magnetization; ionization
Magnetized bubble
Volume Filling Factor of Quasar Bubbles
Magnetic energy density normalized by thermal at 10^4 K
Volume filling factor of IGM
Probability Distribution of Bubble Radius
*Magnetic pressure larger minimum b-parameter of Lya forest
Probability Distribution of Bubble Magnetic Field
*Could account for intra-cluster and galactic fields through adiabatic compression. Explains synchrotron halos of clusters.
B / ú2=3
Key questionsKey questions• Is general relativity the correct description of strong gravity?Is general relativity the correct description of strong gravity?
Do black holes exist?Are they described by the Kerr metric (with the predicted properties of the event horizon, innermost stable circular orbit, photon orbit, etc.)?
• What is the spin and mass distribution of astrophysical black holes? What is the spin and mass distribution of astrophysical black holes? Why?Why?
• What is the history of black hole formation and evolution? What is the history of black hole formation and evolution? How did the first black holes form? How did the first black holes form? Was growth dominated by accretion of gas, consumption of stars or mergers? Do Was growth dominated by accretion of gas, consumption of stars or mergers? Do binaries coalesce? What is the impact of gravitational-wave recoil?binaries coalesce? What is the impact of gravitational-wave recoil?
• How do black holes accrete gas? How do black holes accrete gas? What are the geometry and radiative efficiency of the accretion flow as a function of What are the geometry and radiative efficiency of the accretion flow as a function of the accretion rate? Which fraction of the infalling mass is expelled in outflows?the accretion rate? Which fraction of the infalling mass is expelled in outflows?
• In what form do black holes release accretion energy? In what form do black holes release accretion energy? What is What is the relative fraction of radiation, magnetically-dominated outflows, relativistic the relative fraction of radiation, magnetically-dominated outflows, relativistic particles, non-relativistic winds, neutrinos, gravitational waves?How are relativistic particles, non-relativistic winds, neutrinos, gravitational waves?How are relativistic jets produced? Are they made of e+e- or baryons?jets produced? Are they made of e+e- or baryons?
• How do nuclear black holes influence the evolution of their host How do nuclear black holes influence the evolution of their host galaxies, X-ray clusters, or the larger-scale intergalactic medium?galaxies, X-ray clusters, or the larger-scale intergalactic medium? What is the origin of the correlations between What is the origin of the correlations between black hole mass and spheroid properties?black hole mass and spheroid properties? What sets the maximum mass of galaxies?What sets the maximum mass of galaxies?
The organizing committee will regard this conference as a success if it will result in a new answer to any of these questions…
Dynamics of Black Holes and Dynamics of Black Holes and Stars in Galactic NucleiStars in Galactic Nuclei
Could the close-in massive Starsoriginate in a warm molecular (maser) disk?
• In maser disks:• comparable to the
circumnuclear disk in the Galactic center.• clumps IRS13 complex at 0.12pc • Eccentricity in orbits from stellar interactions.• Heating by X-rays from AGN or by stars.
Milosavljevic & Loeb astro-ph/0401221
T > 400K;n ø 107à 1010cmà 3
M disk ø 104M ì â n9r7=23 T1=2
4 Mà 1=27
Q ü 1
What is the accretion rate into SgrA*horizon?
MçB ø 10à 5M ì yrà 1
Bolometric luminosity: ø 1036erg=s
Mç ø 2â 10à 10M ì yrà 1(ï=0:1)à 1
Bondi rate:
Feeding SgrA* with Stellar Winds
Loeb, astro-ph/0311512
J < J max = ñ c4GM ï
ð ñEmission region:Emission region:
Brownian Motion of a Massive Black Hole in a Stellar System
Chatterjee, Hernquist, & Loeb 2001 (ApJ, PRL)
For a non-Maxwellian distribution function of stars the black hole is not in strict equipartition
Probing the Spacetime Around SgrA* with Pulsars
• BH spin vector from frame-dragging + imaging of pulsar orbit• Inner stellar cluster from gravitational scattering events• Test accretion flow models by measuring plasma density
Pfahl & Loeb 2003 (astro-ph/0309744)
~10-100 massive stars with P<100 yr and lifetime of ~ 107 years~1000 NS in steady state 1-10 detectable pulsars at 10-20 GHz
Laser Interferometer Space Antenna
Binding Energy of Halos
1-sigma 2-sigma
3-sigma
Supernova