Marta Volonteri

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Black holes from the first stars to the Milky Way
Marta Volonteri Astronomy Dept. University of
Michigan
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1. Intro MBHs? Why? When? How? 2. When a bit
of cosmology 3. How paths leading to MBH
formation 4. How growing black holes
MBHMassive Black Hole
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Black holes?
The escape velocity from a black hole is larger
than the speed of light the INSIDE of a black
hole is invisible
Astrophysical black holes are described by 2
parameters only MASS and SPIN Theyre the
simplest objects in the Universe
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Units of measure length parsec (pc) 3x1013
km206,264 Earth-Sun distance
light year distance light travels in 1
year63,000 Earth-Sun distance mass mass of the
sun (Msun)2x1033g 1,000,000 Earth
mass luminosity (energy per unit time)
luminosity of the sun (Lsun)1024 Wtoo many
lightbulbs to count!
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length 10 kpc 32,600 light years mass 1012
solar masses gt one trillion suns! luminosity
1010 solar luminosities
What is a galaxy made of?
Halo dark matter
Disc gasstars
Bulge stars
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Special objects quasars
short for Quasi Stellar objects appear to be
point sources in the sky (pre-Hubble Space
Telescope era)
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QUASARS 1. they are as luminous as galaxies
L1011-1013 Lsun 2. brightness varies on short
timescales (lt1 week)
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3. information is carried at the speed of light
from one side to the other of the source
Sizec x time the emitting region is lt1
light week 1,000,000 times smaller than a
galaxy. NOT galaxies!
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Quasars are powered by black holes
accreting matter 1. they are as luminous as
galaxies Le M c2/time1011-1013 Lsun 2. stars
nuclear fusion e0.007 3. lifetime 107
years ? M108 Msun ? NOT stars! The
implication is the existence of black holes with
masses of millions to billions of Msun
accretion onto a BH e0.1-0.4
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Stellar mass BHs ?formation through stellar
evolution ?mass lt few tens Msun
Massive BHs ? powering quasars ? mass gt 106 Msun
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Where are these Massive Holes?
We can see massive black holes as quasars when
they are eating up some matter... but this not
the whole time!
Hubble Deep Field-North Chandra Deep
Field-North
all galaxies
active galaxies
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MBHs in local galaxies
BHs dominate the motions of stars and gas in a
tiny volume Sphere of influence
Galaxy Size 10-50 kpc
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MBHs in local galaxies
The best example of search for a SMBH is the
MILKY WAY individual stars can be resolved
Massive black holes were also found in the
centers of neighboring galaxies a demography of
MBHs
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MBHs and galaxies
MBHs 106-109 Msun
MBH x1000
BULGE
tiny BHs know about big bulges!
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MBHs and galaxies
MBHs 106-109 Msun
MBH x1000
BULGE
tiny BHs know about big bulges!
RbulgeGMbulge/s2
Rsch2GMBH/c2
s100 km/s c3x105 km/s Mbulge103 MBH
Mhalo10-103 Mbulge
KILOPARSEC
MICROPARSEC
RhaloGMhalo/s2
RinfGMBH/s2
MEGAPARSEC
PARSEC
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length 10 kpc 32,600 light years mass 1012
solar masses gt one trillion suns! luminosity
1010 solar luminosities
What is a galaxy made of?
Halo dark matter
Disc gasstars
Bulge stars
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WHEN do you make a massive black hole?
Quasars have been detected at very large
distances, corresponding to a very young age of
the Universe

• Light, although fast, travels at a finite speed.
• It takes
• 8 minutes to reach us from the Sun
• 32,000 years to reach us from the edge of the
  Milky Way

The farther out we look into the Universe, the
farther back in time we see!
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Quasars have been detected at very large
distances, corresponding to a very young age of
the Universe D c x time Measure D, get
time12.9 billion years ago! Age of the Universe
13.7 billion years
As massive as the largest MBHs today, but when
the Universe was only 1 billion years old!
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1. Intro MBHs? Why? When? How? 2. When a bit
of cosmology 3. How paths leading to MBH
formation 4. How growing black holes
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Cosmological structure formation
The universe after the Big Bang was not
completely uniform Gravitational instability
caused matter to condense until small regions
become gravitationally bound
They then break away from the global expansion,
collapse down on themselves, and form a galaxy at
the center
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This is what we see in cosmological
simulations....
Hierarchical Galaxy Formation small galaxies
collapse first and merge later to form more
massive systems
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1. Intro MBHs? Why? When? How? 2. When a bit
of cosmology 3. How paths leading to MBH
formation 4. How growing black holes
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HOW can you make a massive black hole seed?
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HOW can you make a (super)massive black hole _at_
z10-30?
Direct contraction of a gas cloud into a BH
encounters a couple of problems 1. ANGULAR
MOMENTUM TRANSPORT Because of angular momentum,
collapsing gas clouds become rotationally
supported at 106-8 Schwarzschild radii ? stops
collapsing 2. STAR FORMATION Instead of going
into BH formation, the gas can fragment and form
stars and SNe can blow away the gas reservoir
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PopIII star remnant
DM
DM
gas
gas
One star per galaxy! 100-200 times larger than
the sun
Are the first stars massive enough to collapse
into MBHs?
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HOW can you make a black hole seed?
MBH 103-105 Msun
MBH100 Msun
Direct collapse gas-dynamics (e.g. Haehnelt
Rees 1993, Eisenstein Loeb 1995, Bromm Loeb
2003, Koushiappas et al. 2004, Begelman,
Volonteri Rees 2006, Lodato Natarajan
2006) ?Transport angular momentum on the
dynamical timescale ?Cocoon of dense gas within
which BH forms
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Gas-dynamical direct collapse
DM
DM
gas
gas
unstable
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HOW can you make a black hole seed?
MBH 103-105 Msun
MBH100 Msun
Direct collapse gas-dynamics (e.g. Haehnelt
Rees 1993, Eisenstein Loeb 1995, Bromm Loeb
2003, Koushiappas et al. 2004, Begelman,
Volonteri Rees 2006, Lodato Natarajan
3007) ?Transport angular momentum on the
dynamical timescale ?Cocoon of dense gas within
which BH forms
Runaway collapse stellar dynamics (Devecchi
Volonteri 2008) ?Form dense stellar cluster at
low metallicity ?Stars merge into a super-star,
collapse into BH
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Stellar-dynamics
DM
DM
gas
gas
unstable
Collisions Runaway growth BH
star cluster formation
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1. Intro MBHs? Why? When? How? 2. When a bit
of cosmology 3. How paths leading to MBH
formation 4. How growing black holes
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So, how do these black hole seeds grow?
Mseeds 104 Msun
MMBH106-9 Msun
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protogalaxies
MBHs are grown from protogalactic BH seeds.
These seeds are incorporated in larger and
larger galaxies, along the cosmic merger
history.
time
local galaxy
protogalaxies
local galaxy
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The seeds at zgt20 are small, 100-104 Msun
How do MBH seeds grow to become
supermassive? BH-BH mergers vs gas accretion
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SMBHs and their detectability
ElectroMagnetic bands QUASARS
Gravitational Waves MERGERS
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QUASARS
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And now some exotic stuff...
MBHs mergers and gravitational waves
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Gravity is spacetime curvature. Any
mass/energy bends spacetime near it.
Rapidly moving masses generate fluctuations in
spacetime curvature gravitational waves
When a gravitational wave passes through, space
is stretched and squeezed alternately.
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Dynamical evolution of BH pairs
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Gravitational rocket binary center of mass
recoil during coalescence due to asymmetric
emission of GW
vesc from today galaxies
vesc from high-z galaxies
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• When a gravitational wave passes through, space
  is stretched and squeezed alternately.
• The effect is opposite in perpendicular
  directions.

• Measure the stretching of spacetime ?L using
  lasers

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space based interferometer LISA Joint NASA/ESA
mission ?L10-8 cm for L5 million
km Measuring the diameter of a human hair at the
distance of Mars from the Earth!
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Black holes from the first stars to the Milky Way
? forming the seeds stellar remnants or
collapsed galaxy cores? ? growing the
seeds! ? how we test our predictions
observational signatures