IV : The effects of black holes on Galaxy formation

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IV The effects of black holes on Galaxy
formation

• Prologue
• The M-sigma relation a hint of a connection
  between black hole and galaxy formation
• Basics of galaxy formation
• The Hot Big Bang
• Dark Matter Dynamics
• The main steps of galaxy formation

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IV.1 The mass of supermassive black holes

• Can measure the mass of supermassive black holes
  (SMBHs) by a variaty of techniques
• Direct imaging of stars orbiting the SMBH
  (Galactic Center, Sgr A, only)
• Imagingspectroscopy of central gas disks (HST
  radio-observations of mega-masers)
• Imagingspectroscopy of stellar light
• also, reverberation mapping for AGN

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The Galactic Center
Infra-red (VLT) R.Genzel group (MPA)
X-ray (Chandra) Baganoff (2001)
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M87 (nearby elliptical galaxy)

• Early HST target
• Rotating gas disk at galactic center
• Measured disk rotation implies central object of
  3 billion solar masses!
• Mass cannot be due to normal stars at center not
  enough light is seen.
• Good evidence for 3 billion solar mass black hole.

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M106 (NGC4258)

• M106 (nearby spiral galaxy)
• Contains central gas disk
• Disk produces naturally occuring MASER emission
• Radio telescopes can measure position velocity
  of MASERs to great accuracy.
• Velocity changes with radius precisely as
  expected if all mass is concentrated at center!
• 30 million solar mass black hole

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• Suppose we measure surface brightness and
  (line-of-sight) velocity at each point
• Assume a gravitational potential (including a
  point mass at center)
• Work out all possible stellar orbits
• Populate orbits to best match brightness
  velocity data
• Change the assumed potential and try again
• Find evidence for point mass (SMBH) in all
  nucleated galaxies with good data

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Reverberation (AGN)
Broad lines from matter moving in SMBH potential
they respond to changes in the UV continuum
emission of the AGN
Seyfert-1 galaxy Broad optical lines
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IV.2 The M-sigma relation

• Plot mass of black hole against luminosity (left)
  and velocity dispersion (right) of galactic bulge

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• Find that black hole mass is correlated strongly
  with the velocity dispersion of the bulge (and,
  more weakly, with the luminosity of the bulge)
• Velocity dispersion is most directly related to
  the mass of the galactic bulge
• Extremely important result! Shows that black
  hole growth knows about the properties of the
  galaxy (or maybe galaxy formation knows about the
  black hole??)
• So lets talk about galaxy formation

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Discussion basic ingredients of galaxy formation
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IV.3 Recap of hot big bang

• The big bang (t0)
• Creation of space, time, energy matter
• Extremely high density and temperature
• Universe starts to expand and cool
• Inflation (t10-34 s)
• Period of extremely rapid accelerating
  (exponential) expansion
• Huge expansion leads to extremely homogeneous
  distribution of matter and energy (only
  deviations from homogeneity due to quantum
  fluctuations)
• Nucleosynthesis (t10s to few minutes)
• Universe cools sufficiently for nuclear reactions
  occur result is 76 H, 24 He, traces of other

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• Decoupling (t300,000 years)
• Temperature drops sufficiently that neutral
  hydrogen can form for the first time
• Hence, universe suddenly becomes transparent to
  its own thermal radiation
• Radiation matter decouple radiation redshifted
  and now forms the Cosmic Microwave Background
• Quantum fluctuations from inflation have grown
  under their own gravity to 1 part in 105
• From then on
• Fluctuations continue to grow and form the seeds
  for the formation of galaxies and large scale
  structure

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Penzias Wilson (Bell-Labs)
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NASAs COBE satellite
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Subtract off average level
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Subtract the dipole
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Subtract off the emission from our Galaxy
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The WMAP satellite
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IV.4 Dark Matter Dynamics

• Current day inventory of the universe
• 70 Dark Energy (see later)
• 26 Non-baryonic Dark Matter
• 4 Baryonic Matter (us!)
• From point of view of the formation of large
  scale structure (galaxies and above), dynamics of
  the Dark Matter dominates
• Dark Matter feels mutual gravitational effect
• No other significant interactions!

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Galaxy formation

• Initial stages of galaxy formation
• DM halos from gravitational instability
• Baryonic matter (gas) falls into gravitational
  potential wells of DM halos shocks to the virial
  temperature
• Shocked gas cools via e/m radiation and
  accumulates at the bottom of potential well
• Stars form from dense, cooled gas
• Then
• Final galaxy population shaped by galaxy-galaxy
  mergers