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Galaxies and Cosmology

Galaxies and Cosmology. 5 points, vt-2007 Teacher: Göran Östlin Lecture 6. Distances to galaxies (JL 2.4) - Standard candles (& rods). F = L / 4  d 2 inverse square law  = D / d angular diameter vs distance. Cepheids P-L relation. Cepheid PL relation. Type Ia supernovae.

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Galaxies and Cosmology

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  1. Galaxies and Cosmology 5 points, vt-2007 Teacher: Göran Östlin Lecture 6

  2. Distances to galaxies (JL 2.4)- Standard candles (& rods) F = L / 4  d2 inverse square law  = D / d angular diameter vs distance

  3. Cepheids P-L relation

  4. Cepheid PL relation

  5. Type Ia supernovae Exploding white dwarf MCH=1.44 M Abs mag MB -19

  6. Type II SNe L = 4  R2  T4 for black bodies F1 / F0 = L1 / L0 = R12T14 / R02T04 F1 / F0 observed photometrically T from Black Body approx R1 / R0 from expansion velocity Fainter than Type Ia, less well calibrated

  7. Surface brightness fluctuations

  8. Galaxies and scaling laws Galaxies have broad luminosity function Spirals: Tully-Fisher: L  V4maxinclination Ellipticals: Faber-Jacksson: L  v4 => learn us about galaxies too (3rd) Brightest cluster galaxy Spiral galaxy diameters

  9. Other standard candles… • - Tip of RGB • - Main sequence fitting • eclipsing binaries • Brightest red or blue supergiant • globular cluster luminosity function • planetary nebulae luminosity function • Etc…

  10. Redshift

  11. Redshifts…

  12. Redshisfts… z = (obs - em)/ em = obs / em - 1 =  /  vr = z  c z = H0  d / c => v r= H0  d Valid up to z  0.2 NB Special relativistic formula not more accurate General relativistic description of space-time required

  13. Hubble diagram

  14. Gravitational lens time delay Einstein cross

  15. Cosmic time vs redshift

  16. Complications • Deviations from a pure Hubble flow, peculiar motions • Dust extinction • Malmqvist bias • Evolutionary effects

  17. Acoustic horizon in CMBR

  18. Theoretical cosmology Problems with Newtonian Gravity and Mechanics: Gravity Inertial frames - absolute space and time General Relativity - matter curves space (& time), EP G + g = -8G T / c4 G, g, T are tensors Geometry: line element Cosmological principle: isotropy, homogeneity

  19. Gravity can in General Relativity be regarded as a space curvature rather than a force Orbit of earth a straight line in space-time

  20. Geometrical cosmology: Line elements 2-dim cartesian 3-dim cartesian 3-dim spherical 2-dim curved space Special relativity Timelike separation Null separation (light) Spacelike separation

  21. Robertson-Walker line element Simplest 4-dim (3 space, 1 time) space that fulfills the cosmological principle Only R(t)changes with time -> homogeneously expanding or contracting space

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