Transcript Document

2003
Birth and Dynamics of Galactic Black Holes
• Demography of quiescent black holes in the
present-day universe
• Demography of accreting black holes
(quasars) at early cosmic times
• Dynamics of black holes in galactic centers:
Brownian motion, binaries
• Effects of quasars on their cosmic habitat
Collaborators: Rennan Barkana, Volker Bromm, Pinaki Chatterjee, .
.
Lars Hernquist, Stuart Wyithe
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
Stellar Positions & Motions
Reid et al.
2002
SgrA* in July 1995
Where was Sgr A* in May‘02?
• Sgr A* position: 10 mas
• Star “S2”
seen at pericenter
V ~ 5000 km/s !
Orbit determined
S2’s orbit
• 15 year period
• e = 0.87
• Pericenter
15 mas = 120 AU
. = 17 light-hours
(Schoedel et al 2002)
Ghez et al. 2003
SO-16
closest
approach at
90 AU
Simultaneous fit of orbits implies:
1. BH mass:
(4 æ 0:3) â (d=8kpc) 3 â 106M ì
2. BH proper motion: < 0.8+-0.7 mas/yr
Feeding SgrA* with Stellar Winds
Emission region:
ð
ñ
ï
J < J max = ñ 4GM
c
Loeb, astro-ph/0311512
Sgr A*’s motion
• Continues along
Galactic Plane
• Remove Sun’s motion
V(Sgr A*) < 7 km/s
Reid et al. (2002)
Lower Limit on Sgr A*’s Mass
• Backer & Sramek (1999): MV2 ~ mv2 <energy>
• Reid et al (1999):
MV ~ mv <momentum>
• Chatterjee, Hernquist & Loeb (2002)
mass estimator: a <energy>
Mlim ~ G M(R) m / R V2
• V < 2 km/s a M > 106 Msun
Apparent Deviations from Keplerian Orbits
dt obs = (1 + vk=c)dt
Doppler transformation of time:
a? ;obs =
d 2x ?
dt 2obs
= (1 à
2v k
)
c a?
à
v?
a
c k
BH
star
v
c
ø 10à 2
at
ø 100A:U:
Loeb 2003 (astro-ph/0309716)
Probing the Spacetime Around SgrA* with Pulsars
~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
• 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)
Enclosed Mass
Schoedel et al. 2002
Water Masers: NGC 4258
Moran, Greenhill, &
Herrnstein (2000)
Keplerian Velocity Profile
Miyoshi et al. 1995
Mass densities
Object
Density
Method
(Msun/pc3)
M 87
NGC 4258
Sgr A*
Sgr A*
2 x 106
7 x 109
8 x 1015
2 x 1021
HST:
3x109 Msun in 7 pc
VLBA : H2O 3x107 Msun in 0.1 pc
S16’s orbit
3x106 Msun in 90 AU
Sgr A*s p.m. 1x106 Msun in 1 AU
SMBH
5 x 1025
Rsch
3x106 Msun in 0.05 AU
Correlation between black hole mass and
velocity dispersion of host stellar system
ì = 4:02 æ 0:32; ë
ì = 4:02 æ 0:32; ë = 8:13 æ 0:06
Tremaine et al. 2002
ì = 4:58 æ 0:52
ë = 8:22 æ 0:07
Ferrarese 2002
log(M =M ì ) = ë + ì log(û ?=200km=s)
Quasars Reside in Galaxies
Archeology of the Universe
Earth
distance
The more distant a source is, the more time it takes for its light to reach us. Hence the light
must have been emitted when the universe was younger. By looking at distant sources we
can trace the history of the universe.
Quasars already exist at z~6, only a billion years after the big bang!
Becker et al.
2001
The Earliest Quasar Detected:
z=6.43
Fan et al. 2002
Cosmological Infall Around Quasars at z>6
Barkana & Loeb, Nature, 2003
Lya Line of Quasars
SDSS (Vanden Berk et al. 2001)
HST (Telfer et al. 2002)
ROSAT (Yuan et al. 1998)
Quasar spectrum
ð
8
M BH = 10 M ì
VC
300 km=s
ñ5
Ferrarese et al. 2002
Tremaine et al. 2002
Wyithe & Loeb 2002
z = 4:80
M BH = 4:6 â 108M ì
M = 2:5 â 1012M ì
z = 6:28
M BH = 1:9 â 109M ì
M = 4:0 â 1012M ì
SDSS 1122 à 0229
SDSS 1030 + 0524
SDSS 1122 à 0229
SDSS 1030 + 0524
SDSS 1122 à 0229
SDSS 1030 + 0524
Basic Facts About the Universe
• On large scales our universe is simple:
HOMOGENEOUS:
the same everywhere
HOMOGENEOUS
Observer 1
Observer 3
Observer 2
ISOTROPIC:
the same in all directions
Direction1
Direction 2
Earth
Direction 3
But on small scales the universe is clumpy
Early times
Mean
Density
Intermediate times
Late times
Formation of Massive Black Holes in the First Galaxies
õ = 0:05
H 2 suppressed
Add Bromm
R < 1pc
M 1 ø 2:2 â 106M ì
M 2 ø 3:1 â 106M ì
Low-spin systems: Eisenstein & Loeb 1995
Numerical simulations: Bromm & Loeb 2002
Eddington Limit
Gravitational force per proton:
BH
gas
GM m p=r 2
Radiation force per electron:
accretion
2
(L =4ùr c)û T
For a spherical geometry, the outward radiation force balances the
inward gravitational force at the Eddington luminosity:
L E = (4ùGM m pc=û T) = 1:4 â 1046(M =108M ì )erg=s
Accretion of fuel is possible only if
L < LE
Self-regulation of Supermassive Black Hole Growth
quasar
L t dyn ø 32M gasû 2
halo velocity dispersion
maxf L g = L E / M bh
dynamical time of galactic disk
!
M bh
108M ì
After translating û !
û?
ð
= 1:5
ñ5
û
200km=s
this relation matches the
observed M à û ã correlation
in nearby galaxies (Tremaine
et al. 2002; Ferarrese &
Merritt 2002)
Silk &Rees 1998; Wyithe & Loeb 2003
Quasar Luminosity Function
Simple physical model:
*Each galaxy merger leads to a bright quasar phase during which the black hole
grows to a mass M ï / v5c
and shines at the Eddington limit. The duration of this
bright phase is proportional to the (smaller than unity) mass ratio in the merger.
*Merger rate: based on the extended Press-Schechter model in a LCDM cosmology.
duty cycle ~10 Myr
Wyithe & Loeb 2002
Did the most massive galaxies form at z>6,
only a billion years after the Big-Bang?
Stars=collisionless fluid
late accretion
Core of CDM halos
stabilizes at z~6
Loeb & Peebles 2002
Proposal confirmed by N-body simulations
Gao Liang &
Simon White
(2003)
Loeb & Peebles 2002
Brownian Motion of a Massive Black Hole in a Stellar System
For a non-Maxwellian
distribution function of
stars the black hole is not
in strict equipartition
Chatterjee, Hernquist, &
Loeb 2001 (ApJ, PRL)
Black Hole Binaries due to Galaxy Mergers
X-ray Image of a binary black hole system in NGC 6240
10kpc
z=0.025
Komossa et al. 2002
Dynamics of black hole binaries
R
Figure1.ps
Numerical
experiment:
400,000 stars
M/M*=0.25%
Typical binaries coalesce in less than 10 Gyr due to wandering
Chatterjee, Hernquist, & Loeb 2002
Open issue: kick velocity
Laser Interferometer Space Antenna
Gravitational Wave Amplitude from a Black Hole Binary at z=1
Gravitational Radiation from Coalescence of
Massive Black Hole Binaries
PULSARS
LISA
REDSHIFT
FREQUENCY (Hz)
Wyithe & Loeb 2002
Environmental Effects of Quasars
Radiative: ionization of intergalactic hydrogen and helium
Hydrodynamic: powerful relativistic outflows
Spectrum of a High Redshift Quasar
(z=5.73)
Djorgovski et al. 2001, ApJL, submitted
Transmitted flux ---> HI/HII<1e-6
(Fan et al. 2000)
On the Threshold of the Reionization Epoch
Djorgovski et al. 2001
Structure Formation in the IGM
Density contrast of gas at z=0 for a
100x100x10 Mpc^3 slice
Density contrast of gas shocked
between z=0.14-0.09
Evolutionary Stages of Reionization
• Pre-overlap
• Overlap
• Post-overlap
neutral H
Ionized H
Reionization Histories of H, He
Free Parameters:
(i) transition redshift, z_tran,
zt ran above which the stellar IMF is
dominated by massive, zero-metallicity stars; (ii) the product of the star formation
efficiency and the escape fraction of ionizing photons in galaxies, f escf ? .
FILLING
FRACTION
H+
He+
REDSHIFT
He++
Quasar model fits luminosity function data up to z=6
Wyithe & Loeb 2002
Quasars as Perturbers:
Impact of Quasar Outflows on the IGM
small-scale structure; magnetization; ionization
BAL outflow
jet
Magnetized
bubble
quasar
Intergalactic Medium (IGM)
Is the IGM fully magnetized just like the ISM?
Furlanetto & Loeb 2001
Volume Filling Factor of Quasar Bubbles
Volume
filling
factor of
IGM
Magnetic
energy
density
normalized
by thermal
at 10^4 K
Probability Distribution of Bubble Magnetic Field
*Could account for intra-cluster and galactic fields through B / ú2=3
adiabatic compression. Explains synchrotron halos of clusters.
Injection of Positrons from AGN Jets
e+ejet
AGN
Furlanetto& Loeb 2002
Spectrum of Positron Annihilation Line
3-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)
What fraction of the earliest quasars is being
gravitationally lensed?
- PS Halos
- -No evolution
OCDM
LCDM
SCDM
Barkana &
Loeb 2000
Are the Highest-Redshift Quasars Gravitationally Lensed?
4 SDSS Quasars with z>5.73
Observer
Lensing Galaxy
Quasar
Wyithe & Loeb,
Nature 2002
Time
Delay
= (gravitational +geometric)
Excess magnification due to
stars next to one of the images
Magnifying the Broad Line Region of
Quasars with Stellar Microlenses
Quasar accretion disk
Wyithe & Loeb 2002
(source of continuum emission)
Observed Time-Delay Lightcurves
RX J0911+05
SBS 1520+530
Burud et al. 2002
Anomalies of Time-Delay Lightcurves
Observations: up to a few percent variations on tens to hundreds of days
Observed anomalies in RX J0911+05 & SBS 1520+530 by Burud et al. (2002) ---> N<10^6
Lack of anomalies in Q2237+0305 ---> N>10^4
Inferred cloud number is consistent with bloated star model (Alexander & Netzer 1997)
The Future of the Intergalactic Medium
ÒË = 0:7; Òm = 0:3
(Recombination time)>>(Hubble time) outside collapsed objects today.
This inequality will get much stronger in the future because the IGM
density will be diluted exponentially with cosmic time.
Future Evolution of Nearby Large-Scale Structure
Coma
Great
Attractor Perseus
Pisces
Nagamine
& Loeb
2002
The Long Term Future of Extragalactic Astronomy
Accelerating
source
c
us
Loeb 2002, PRD; astro-ph/0107568
Analogy
Ants = Photons
Balloon=Expanding Space
Analogy
Ants = Photons
Balloon=Expanding Space
visited area
(horizon)
since blowing
started
(Big Bang)
Analogy
Ants = Photons
Balloon=Expanding Space
visited area
(horizon)
since the
blowing began
(Big Bang)
Ants can be separated at a rate much larger
than their own walking speed
Maximum Visible Age
All sources above a redshift of 1.8 are already out of
causal contact with us!
How many galaxes will reside within
our event horizon in 100 billion years?
Answer: one
(the merger product of the Andromeda and
Milky-Way galaxies)
Ejection of Stelar Mass Black Holes from Globular Clusters
star-star
star-BH
BH-BH
ejection
Chatterjee, Loeb & Haernquist 2003
Bright quasars reside in massive galaxies:
Spectral Signature of Cosmological Infall Around the First Quasars
infall
observer
accretion
shock
virialized
gas
redshifted
accretion
shock
Barkana & Loeb, Nature, 2003; astro-ph/0209515
Simulation of
Reionization
z=11.5
Ionizing Background
log(f_HI)
Gnedin (2000)
log T
log(gas density)
z=7
z=4.9
For comprehensive reviews on Reionization, see:
*Barkana & Loeb 2001, Physics Reports 349, 125
*Loeb & Barkana 2001, ARA&A, 39 (Sep. 15)
Collapse Redshift of Halos
Atomic cooling
H_2 cooling
1-sigma
2-sigma
2-sigma
3-sigma
Probability Distribution of Bubble Radius
*Magnetic pressure
larger minimum b-parameter of Lya forest
Redshift and Splitting Distributions of Lenses
- LCDM
z_s=5
z_s=2
- - OCDM
… SCDM
z_s=10
z_s=5
z_s=10
Flux from Lensing Galaxy in G-P Trough
z_s~6
22.2
23.3
I*=22.2
SDSS at z=6.28
Alternative Interpretations of Lightcurve Anomalies
(Gould & Miralda-Escude 1997)
Hot spots in
accretion disk
Black
Hole
Hotspots: timescales are too
short compared to observations!
Second Alternative:Microlensing by Planets
(Schild 1996)
Accretion disk
Motion in 10 years with a transverse velocity of 400 km/s
Planets: (Also,
timescales
are
too
long!
ruled out by the MACHO search).
ü / ú2R 2
/ (1 + z) 4
Spectrum of a Source Just Beyond the Reionization Redshift
Absorption Spectrum
A Simple Explanation
Explain: binding enrgy per
dynamical time
Laser Interferometer Space Antenna (LISA)
Future Prospects
3/2
• Vlim ~ 1/t
• Mlim ~ 1/V2lim <energy>
~ t3
• When Vlim ~ 2 km/s (~2007),
Mlim ~ 106 Msun
• Could show ALL mass in Sgr A* !
Reid 2002