Supermassive Black Holes

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Supermassive Black Holes their Host Galaxies

• Ilana Klamer
• CSIRO ATNF

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Todays discussion

• Some concepts
• Supermassive black holes
• The host galaxies
• Active galaxies
• Formation of SMBHs
• Formation of massive galaxies
• The current paradigm
• and its problems
• Where to from here?

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Cosmological Distances
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Sydney to Antofagasta 24 hours to
Antofagasta 0.04 seconds to Venus
4.3 minutes to Sun
8.3 minutes to V465 Cen 4.2
years to Canis Major 25 000 years to
UDF00452 12.8 billion years
X
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REDSHIFT(i) Doppler (relative motion)(ii)
Cosmological (expansion of space-time)(iii)
Gravitational (bending of space-time)
a shift in the frequency of a photon toward lower
energy, longer wavelength, lower frequency.
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(i) Doppler Redshift
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• Spectral lines from receding side of galaxy
  will be REDSHIFTED wrt local velocity of the
  galaxy whilst approaching spectral lines will be
  BLUESHIFTED

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(ii) Cosmological Redshift
H?
H?
H?
z0.25 (D986 Mpc)
H?
H?
H?
H?
z0.06 (D247 Mpc)
H?
H?
H?
H?
z0.02 (D83 Mpc)
H?
H?
H?
H?
z0
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(iii) Gravitational Redshift
Space-time bends in the presence of mass (a
strong gravitational field). Light, in order to
escape gravity, must expend energy to climb out
of the gravitational field.
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Supermassive Black Holes

• A black hole is a region of space-time from which
  nothing can escape from, not even light

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Black Holes

• Reverend John Michell (1783) - concept first
  proposed
• That gravity could effect light as well as matter
• Schwarzschild (1913) - derived formalism for the
  singularity
• Using Einstein field equations
• Chandrasekhar (1931) paper rejected by ApJ
• A star of large mass cannot pass into the white
  dwarf stage, one is left speculating on other
  possibilities
• Eddington the authority
• a star would have to go on radiating and
  radiating, and contracting and contracting.I
  think there should be a law of nature to stop
  matter behaving in this absurd way
• Oppenheimer (1939) exercise in abstraction
• the star closes itself off from any
  communicationonly its gravitational field
  persists

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Discovery of Quasars (1963)

• The Lunar Occultation of 3C273
• Parkes Observatory identifies a strong radio
  source with a bright (13th magnitude) star
• A few of these weird stars already known
• variable light so couldnt be extragalactic

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• Schmidt interprets spectrum as cosmological
  redshift z0.158
• Only a black hole could provide this energy

Observational cosmology is born
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The black hole at the centre of the Milky Way
(Sgr A)
NGC 1232- resembles our Milky Way
2x105 light-years across (2xMW) 70x106
light-years away
1 light year 1,000,000,000,000 km
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Our black hole (Sgr A)
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Our black hole (Sgr A)
Simultaneous fits to all the stellar orbits
yields a dark object which is 3.6 million solar
masses and confined to 8.5 light-hours in radius
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Orbital motion under gravity
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Black holes in other galaxies NGC 4258

• Observed bright maser lines from rapidly rotating
  disk
• Rotation purely Newtonian- 40 million solar mass
  central object
• Extreme energies from the rotation can only come
  from a BH

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And another one 1.2 billion solar masses
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Very high redshift Quasars
Ly-? 121.6 nm Observed 885nm z 6.3 12.7
billion light years
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Weighing a black hole

• Binary systems (only good for small black holes
  orbiting around another star)
• Proper motion of stars around black hole (only
  done for Sag A)
• Rotation curves based on Maser emission lines
  from central accretion disk (NGC 4258 only)

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other measurements

• Rotation curves for gas
• Velocity dispersion for stars

Velocity (km/sec)
M3 billion solar masses
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Reverberation mapping

• Based on a time delay between the continuum and
  emission line variations

Velocity (km/sec)
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The host galaxies of supermassive black holes
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The Hubble sequence
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Spiral galaxies

• NGC1232
• young blue stars, and dark dust
• Spectra dominated by light from stars.

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Elliptical Galaxies

• They are the most massive galaxies known at
  present (5000 billion solar masses)
• Optical spectra dominated by old M and K stars
• Their stars formed billions of years ago

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The host galaxies

• Massive black holes are at the centre of most
  galaxies (we already discussed this)
• The black hole mass is intimately related to the
  host galaxy mass
• i.e. the most massive black holes reside in the
  most massive galaxies

Black Hole Mass
Host Galaxy Mass
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What have we discussed so far?

• Space-time is curved by the matter (energy). In
  the vicinity of an extremely massive object, the
  curvature is so great that even light cannot
  escape and will be dragged back by its
  gravitational field. This is a black hole.
• Since the discovery of quasars, we have had
  observational evidence exists for supermassive
  black holes at the centre of galaxies (I showed
  examples of Milky Way, NGC 4258, NGC4261)
• It is now believed that supermassive black holes
  reside at the centre of most (all?) galaxies.
• The masses of nearby host galaxies are
  proportional to the central black hole mass.
• It is not clear that high-redshift (young)
  galaxies also display the same proportionality.

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Questions?
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Active galaxies
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Seyfert galaxies

• NGC 4151- a spiral
• Spectrum is underlying spiral type (stars) plus
  emission lines from central AGN

Black hole masses 107-8 Msun
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Radio Galaxies
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Centaurus A
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The CALOSIS project

• CentaurusA Long Overdue Synthesis Imaging Survey

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Formation and evolution of supermassive black
holes their host galaxies
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The cosmic microwave background

• Big Bang
• (a tongue-in-cheek name given to the birth of the
  universe by Fred Hoyle)
• Universe was born a hot plasma filled with e, s,
  photons.
• too hot to combine and photons Thomson scattered
  off the plasma.
• As universe expands and cools to about 3000K, e
  and p recombine to form H and photons can escape.
  This is at z1088 surface of last scattering
• The photons have been redshifted down to 2.7K
• 1948 Gamow, Alpher Hermann even predicted the
  CMB at 5K (28K later)
• 1965 Penzias Wilson build a radiometer but
  cant account for 3.5K excess
• Robert Dicke, Princeton Boys, weve been
  scooped!
• Won Nobel Prize in 1978

Penzias Wilsons horn antenna
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• COBE Satellite confirms the BB nature of CMB
  the anisotropies associated with the surface of
  last scattering.
• CMB isotropic to 1 part in 100,000.
• Nobel Prize in Physics 2006 to Mather Smoot
• "for their discovery of the blackbody form and
  anisotropy of the cosmic microwave background
  radiation
• WMAP satellite is doing precision cosmology
  with finer detail studies of the anisotropies

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The initial conditions of the Universe can be
summarized on a single sheet of paper, yet they
developed into the complex structures we see
today
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The origin of structure
Time since Big Bang
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The Universe
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The first objects Pop III stars

• Overdensities collapse and form first stars made
  of primordial gas
• These are very massive and will collapse into
  black holes
• These black holes grow by factors of a million in
  less than a billion years how?
• Supermassive black holes detected 800 million
  years after the Big Bang.

BEWARE! these are simulations, predictions and
theory. Pop III stars have not yet been detected
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setting the scene
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• Star Formation today
• Gravitational collapse of cold dense clouds of
  gas
• Complex highly inhomogeneous structures
• Gravity v turbulence and magnetic fields
• We still lack a comprehensive theoretical
  framework that predicts the IMF from first
  principles.
• )

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Star Formation in the Early Universe

• Early Universe is much simpler?
• Primordial gas left from big bang nucleosynthesis
• H (75), He (25)
• Absence of heavy elements and dust
• No previous star formation
• Magnetic fields weak/not dynamically important
• 10-30 G compared with 10-6 G for spiral galaxies
• May be easier to model, but why/how does it
  happen at all?

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Star Formation in the Early Universe

• Need cooling timescales ltdynamical timescales (or
  form a BH directly)
• Most simulations, regardless of the initial
  conditions, produce lt1000K 106 Msun primordial
  clouds
• These are gt10x lower than the atomic H cooling
  threshold
• In the absence of all else, primordial gas must
  cool via H2
• But since there is no dust, this must be in gas
  phase only
• Free electrons or protons are required as
  catalyst, or some other direct process to ionise
  the atomic H

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Star Formation in the Early Universe

• LW (11.2-13.6eV) radiation from Pop III stars
  will photo-dissociate the H2 suppressing further
  star formation.
• Need enhanced abundances of e- or e to enhance
  the H2 fraction reduce the negative UV
  feedback
• X-ray photons from supernova remnants
• Accretion onto black holes
• free electrons in HII region
• collisional ionisation in shock waves
• relativistic plasma from AGN jets

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Formation of supermassive black holes

• The existence of 109 Msun SMBHs within 109 years
  of the Big Bang provides strong constraints on
  any galaxy/BH formation models.
• Growth/mergers/accretion of 100-1000Msun Pop III
  black holes
• Direct collapse of 108 Msun gas clouds below
  critical enrichment levels of order Z-3.5 Zsun
  with suppressed H2 cooling -gt BHs with average
  masses 5x104 Msun at zgt10.
• Growth/mergers/accretion of above BH mass halos

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Galaxy formation

• Hierarchical formation (e.g lCDM)
• Small things merge or coalesce to form larger
  things
• This includes galaxies and black holes
• Model explains large scale structure and is
  consistent with primordial fluctuations in the
  CMB radiation.
• Consequence/Implication/Prediction
• massive objects form last and do not exist in the
  early universe

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We are clearly on the right track
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We are clearly on the right track
But it cant explain everything yet?
Latest results from WMAP showing the structure in
the CMB radiation
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Luminosity Functions

• The most challenging outstanding problem in
  galaxy formation is to explain the shape of the
  luminosity function
• the number of galaxies in L, L?L per unit
  volume.

faint end
faint end
bright end
bright end
data with original model prediction too many
high L and low L galaxies
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Reproducing the mass function
What are these massive galaxies?
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There are quasars,
radio galaxies,
and old ellipticals
SCUBA galaxies,
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The problem with hierarchical formation

• Reproducing the luminosity functions
• Too many massive galaxies too early on
• Too much star formation too early on
• Too many supermassive black holes too early on
• Too much chemical enrichment too early on
• Too many satellite galaxies by a factor of 100

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The end for ?CDM?
Slide adapted from Richard Ellis (Caltech)
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Fixing ?CDM

• The models dont agree with the observations.
• Do you
• 1. Add extra parameters to the models to fit the
  observations?
• 2. Find new models through scientific process?

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data with original model prediction too many
high L and low L galaxies
thermal conduction
energy injection
superwinds
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Negative feedback

• Radio jets (from AGN) heat the IGM and blowing
  gas out from the centre of the galaxy.

Perseus A in X-rays radio
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Fixing the luminosity functionwith negative
feedback
Tah Dah!
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Or, should we start to consider another paradigm?

• Remember that
• Mergers are clearly important
• Large Scale structure well explained
• Physics strongly prefers hierachical formation
• So what have we left out?
• Plenty! e.g. magnetic fields, masses of Pop III
  stars, chemical enrichment
• Effects of the black hole energetics

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Positive AGN feedback

• Massive galaxies form faster than we think
• Massive black holes exist earlier than we think
• Black holes form first (suppressed H2 formation)
  and then hasten the formation of their galaxies
  (provide enhanced production of H2)
• This is called positive FEEDBACK
• (negative feedback is when the energy from the
  quasar halts the formation of the host galaxy)

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Breakdown of M-? at high redshift?

• Observations of high redshift radio galaxies
  suggest a SMBH is in place before the host
  galaxies form.
• Recent measurements of the gas content in
  SDSSJ11485251 at z6.41 leave little room for a
  host galaxy which agrees with the M-s relation.

Mtot40-50 billion

Mgal3 trillion ???


Mbh3 billion
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Examples of positive feedback e.g. Minkowskis
Object NGC 541
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Positive Feedback in the early universe

• UV (rest frame)
• UV (rest frame)
• Ly-a

Unpolarised shows absorption lines P-Cygni
type profiles similar to SF galaxies
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Todays discussion (I hope!)

• Some concepts
• Supermassive black holes
• The host galaxies
• Active galaxies
• Formation of SMBHs
• Formation of massive galaxies
• The current paradigm
• and its problems
• Where to from here?

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questions/comments?