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Cosmology : Cosmic Microwave Background & Large scale structure

Cosmology : Cosmic Microwave Background & Large scale structure. Lec . 1: Background universe. Cosmology IUCAA VSP program ( May 18-22, 2012). Tarun Souradeep. I.U.C.A.A . The Realm of Cosmology. Basic unit: Galaxy. Size : 10-100 kilo parsec (kpc.)

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Cosmology : Cosmic Microwave Background & Large scale structure

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  1. Cosmology : Cosmic Microwave Background & Large scale structure Lec. 1: Background universe Cosmology IUCAA VSP program (May 18-22, 2012) Tarun Souradeep I.U.C.A.A.

  2. The Realm of Cosmology Basic unit: Galaxy Size : 10-100 kilo parsec (kpc.) Mass : 100 billion Stars Measure distances in light travel time 1 pc. (parsec) = 200,000 AU = 3.26 light yr. Measure Mass in Solar mass Andromeda Galaxy

  3. The Realm of Cosmology 100 million Light years

  4. The Realm of Cosmology 500 million Light years

  5. The Realm of Cosmology 5 Billion Light years

  6. The Realm of Cosmology

  7. How can we even hope to comprehend this immensely large& complex Universe !?! Look for an appropriate simple model

  8. Modeling nature Picasso: Steiren series

  9. The Isotropic Universe Distribution of galaxies on the sky is broadly isotropic • Isotropy around every point • implies • Homogeneity • Cosmological principle • FLRW models South North Lick Observatory survey

  10. The Expanding Universe Leads to the Hubble’s law Recession velocity is Proportional to the distance Matter density: 1/V Radiation density: 1/(V L) Early Universe is radiation dominated E Einstein’s General relativity applied to an uniform distribution of matter on cosmic scales leads to a smooth expanding universe (FRW Cosmology) Fig.: Ned Wright

  11. The Expanding Universe Fig.: Ned Wright

  12. Space-time of the cosmos Fig.: Ned Wright

  13. Space-time of the cosmos General relativity allows us to formulate physics in any coordinates Fig.: Ned Wright

  14. Space-time of the cosmos Comoving spatial coordinates Fig.: Ned Wright

  15. Space-time of the cosmos Conformal time Comoving spatial coordinates Fig.: Ned Wright

  16. Cosmological Redshift Observer Distant galaxy Equal time events at a distant galaxy appears time-dilated Frequency of light from a distant galaxy is scaled by the expansion  Redshift, z=v/c Redshift is related to distance Fig.: adapted from Ned Wright

  17. Expanding Universe Hubble’s law: Recession velocity of galaxies is proportional to the distance Hubble’s measurements in 1929 Frequency of light from a distant galaxy  Redshift, z=v/c Redshift is related to distance Fig.: Ned Wright

  18. Expanding Universe Hubble’s Law: Current observational status Fig.: Ned Wright

  19. Cosmic Microwave Background Pristine relic of a hot, dense & smooth early universe - Hot Big Bang model Post-recombination :Freely propagating through (weakly perturbed) homogeneous & isotropic cosmos. Pre-recombination : Tightly coupled to, and in thermal equilibrium with, ionized matter. (text background: W. Hu)

  20. Cosmic “Super–IMAX” theater 0.5 Mega-years 43 Billion Light-years Here & Now (14 Giga-years) Transparent universe Opaque universe

  21. The Isotropic Universe Cosmic Microwave Background Nobel prize 1978 Serendipitous discovery of the dominant Radiation content of the universe as an extremely isotropic, Black-body bath at temperature T0=2.725 (+/-0.002)K . “Clinching support for Hot Big Bang model”

  22. Cosmic Microwave Background The dominant radiation component in the universe ~ 400 CMB photons per cubic cm. (D. Scott ’99)

  23. “Dust” in an expanding box Size = ¼ Number density x 64 Energy density x 64 Size = ½ Number density x 8 Energy density x 8 time Radiation in an expanding box Matter density: 1/V Radiation density: 1/(V L) Early Universe is radiation dominated E Size = ¼ Number density x 64 Energy density x 128 Temperature x 4 Size = ½ Number density x 8 Energy density x 16 Temperature x 2 time

  24. Cosmic Microwave Background The most perfect Black-Body spectrum in nature COBE –FIRAS The CMB temperature – A single number characterizes the radiation content of the universe!! COBE website

  25. Baryons: Big Bang Nucleosynthesis

  26. Baryons: Big Bang Nucleosynthesis

  27. Geometry of the Universe Spherical Universe Constant positive curvature Hyperbolic Universe Constant negative curvature Flat Universe

  28. Friedman equations

  29. Evolution of density

  30. `Standard’ cosmological model: Geometry, Expansion & Matter Clustering matter Non-Clustering matter

  31. How much do we now know about this model Universe ? lots !!!

  32. Good old Cosmology, … New trend ! Total energy density Baryonic matter density Dark energy density Expansion rate of the universe Dark matter density Age of the universe NASA/WMAP science team

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