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

Andromeda Galaxy The Realm of Cosmology Basic unit: Galaxy Size : 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

The Realm of Cosmology 100 million Light years

The Realm of Cosmology 500 million Light years

The Realm of Cosmology 5 Billion Light years

The Realm of Cosmology

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

Modeling nature Picasso: Steiren series

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

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

The Expanding Universe Fig.: Ned Wright

Space-time of the cosmos Fig.: Ned Wright

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

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

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

Observer Distant galaxy Equal time events at a distant galaxy appears time-dilated Cosmological Redshift 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

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

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

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

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

The Isotropic Universe T 0 =2.725 (+/-0.002)K. Serendipitous discovery of the dominant Radiation content of the universe as an extremely isotropic, Black-body bath at temperature T 0 =2.725 (+/-0.002)K. “Clinching support for Hot Big Bang model” Nobel prize 1978 Cosmic Microwave Background

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

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

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

Baryons: Big Bang Nucleosynthesis

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

Friedman equations

Evolution of density

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

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

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