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Galaxies and Cosmology

Galaxies and Cosmology. 5 points, vt-2007 Teacher: Göran Östlin Lecture 12. Lecture 12 contents. Cosmological problems Observational Cosmology: - Galaxy formation and evolution: from pop III to today - Cosmological parameters: H 0 , q 0 , Ω (bar, matter, DM), T 0

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Galaxies and Cosmology

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  1. Galaxies and Cosmology 5 points, vt-2007 Teacher: Göran Östlin Lecture 12

  2. Lecture 12 contents • Cosmological problems • Observational Cosmology: - Galaxy formation and evolution: from popIII to today - Cosmological parameters: H0, q0, Ω (bar, matter, DM), T0 • Summary of course

  3. Problems with standard BBI. Magnetic Monopoles What is a monopole? - magnetic charge Where are they?

  4. Problems with standard BBII. Horizon problem

  5. Problems with standard BBIII. Flatness Problem k is independent of R and time, but Ω rapidly approaches the value 1.0 for small R Alternatively: if k0 one would expect Ω0 << 1 or Ω0 >> 1 To be compatible with todays Ω0 which is of order one, then Ω(tPlanck) must have been = 1.000…(55 zeros)..001 -Enormous fine tuning!

  6. Problems with standard BBIV. Origin of structure Inflation enlarges the scale of quantum fluctuations Microscopic Becomes Macroscopic

  7. Evolution of R during inflation

  8. What could have caused inflation? Equation of state: p = w  Radiation: w=1/3 Matter: w0 If w<-1/3 we would get acceleration i.e. Negative pressure makes gravity repulsive! Could w be a function of time? quintessence

  9. Problems with standard BBIV. Origin of structure Inflation enlarges the scale of quantum fluctuations Microscopic Becomes Macroscopic

  10. The nature of dark matter Baryonic dark matter Hot vs cold non-baryonic dark matter: e.g. Nutrinos vs WIMPs

  11. Nature of dark energy • Cosmological constant • Vaccuum energy • Quintessence • String/Brane theory, extra dimensions • The anthropic principle • is the universe there for us or do we exist because the universe looks like it does • Science of philosophy?

  12. Structure/galaxy formation The concept of Jeans mass Gravity vs pressure, Static medium: M > Mjeans exponential growth Expanding EdS: M > Mjeans linear growth Expanding Open universe: M > Mjeans no growth Fluctuation spectrum: EdS: temperature fluctuations in CMBR expected at the 10-3 level, but only 10-5 observed Dark matter comes to rescue!

  13. Evolution of Jeans mass with scale factor with scale factor R

  14. observations Numerical simulation

  15. Hierarchical growth of structure Galaxy formation is a continous process Each big galaxy has had one major merger since z=1

  16. Post-recombination evolution of the Jeans mass

  17. Observations of the distant universe HST Ultra Deep Field 2 weeks of exposure Most distant galaxies at z=6 Problem: most of the light comes out in the infrared

  18. Lookback time and age

  19. Luminosity distance and angular size distance

  20. Redshifting galaxies LBGs LyaGs EROs

  21. Closing in on the dark ages…

  22. ”Madau-plot”

  23. Madau plot is very sensitive to asssumptions about dust

  24. Hierarchical growth of structure Galaxy formation is a continous process Each big galaxy has had one major merger since z=1

  25. AGN feedback Different phases of the merger of two galaxies with central supermassive black holes. From top to bottom, the individual images of the sequence show the gas of two colliding spiral galaxies. After the first encounter, they first separate again from each other, but then come together for a second encounter and subsequent coalescence. Gravity is driving gas into the centers of the galaxies and leads to the formation of extended tidal arms. As a result of the nuclear inflow, the black holes grow strongly in mass during a quasar phase. This phase lasts up to 100 million years and releases enough energy to heat the gas and to expel it into extragalactic space. At the end an elliptical galaxy remains (its stars are not shown in the image sequence) which contains almost no residual gas and hosts at its center the merged pair of supermassive black holes.

  26. JWST

  27. Some future observational tools ALMA, sub-mm, 64 antennae JWST “the first light machine” 6.5 m OWL the overwhelmingly large telescope +50m

  28. Cosmological parameters The quest for 3 (4) numbers….

  29. Properties of the Universe set by 3 parameters: m, , k of Which only 2 are Independent: m + + k = 1

  30. CMBR fluctuations First acoustic peak = standard rod! Height set by ΩBaryon At larger scales: Sachs-Wolfe

  31. Supernova Ia Measures q0 Q0 = Ω0,M/2 + Ω0,

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