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. 2: Cosmic Content Perturbed Universe

Simple … yet, an exotic universe 95% of the energy of the universe is in some exotic form Dark Matter: we cannot see it directly, only via its gravitational affect. Clusters under gravity. 73% Dark Energy: smooth form of energy that we cannot repulsively under gravity. 23% Ordinary (baryonic) matter accounts for 4% Know 99% the radiation content of the universe (CMB) Insignificant now (0.01%) but important prior to z<10000

Evolution of thought: Matter budget of the cosmos Fig:NASA/WMAP science team

Matter budget of the Universe w=0 Decelerated Expansion (Grav. Clustering) w=0 (w<-1/3) Decelerated Expansion (Non-Clustering)

Ordinary matter is sprinkled on the Cold Dark matter distribution Galaxies light up at the densest points

Where is the Cold Dark matter ? 6 times more in dark matter than ‘baryonic’ matter Zwicky 1935

Dark matter in Galaxies ! R

Rotation of Spiral Galaxies !!!

Dark matter in our own backyard !?!

Dark matter in the Milky way

Dark matter in other galaxies too !!

Dark matter in clusters !?!

Hot gas in clusters Coma cluster

Hot gas in clusters Virgo cluster

Marbles in a glass bowl !!! Velocity dispersion of galaxies in a cluster Measures the depth of its gravitational potential Speeding galaxies in a cluster

Gravitational lensing Distant galaxies beyond a cluster are lensed….

Bullet cluster

movie

Evidence for Dark Energy? Is it the Cosmological constant? The Cosmic repulsive force Einstein once proposed and later denounced as his ‘biggest blunder” ?

Theoretical possibilities Possibility 1: Universe permeated by energy density, constant in time and uniform in space (Einstein’s  ). Possibility 2: DE some kind of ‘unknown’ dynamical fluid. Its eqn of state varies with time (or redshift z or a  (  z )  ). Impact of DE (or different theories) can be expressed in terms of different “evolution of equation of state” w ( a )  p ( a ) /  ( a ) with w ( a )  for  Possibility 3: GR incorrect, modified Lagrangian, Braneworld scenario (higher derivative/dimensional gravity) Possibility 4 : `Inhomogeneous’ cosmos – backreaction of gravitational. Instability (UNLIKELY)

Geometry, Expansion & Matter Dark energy causes accelerated expansion

Correction to the Hubble’s Law …. measures the acceleration in the expansion of the universe Measure distances independent of redshift v/c till v/c=z~1

10 m Flux 5 m Measuring distance using standard candles 4 Flux

Supernova in a galaxy: standard candle

Supernova can be seen in distant galaxies

Supernova in a very distant galaxy

Starlight from Galaxies Stuff we are made of!! Light elements from early hot universe Low CMB temperature fluctuations Accelerated expansion of the universe (High redshift SN) Structure formation scenario compatible with observations Rotation of galaxies Speeding galaxies in clusters Gravitational lensing Hot gas in clusters Matter budget of the cosmos Fig:NASA/WMAP science team

How do we know so much now about this model Universe ? Perturbed universe!

Transparent universe Opaque universe 14 GPc Here & Now (14 Gyr) 0.5 Myr Cosmic “Super–IMAX” theater

After 25 years of intense search, tiny variations (~10 p.p.m.) of CMB temperature sky map finally discovered. “Holy grail of structure formation” Predicted as precursors to the observed large scale structure The Perturbed Universe Cosmic Microwave Background Anisotropy

George Smoot John Mather COBE Cosmic Background Explorer First detection of CMB anisotropy (1992)

Temperature anisotropy T + two polarization modes E&B Four CMB spectra : C l TT, C l EE,C l BB,C l TE CMB Anisotropy & Polarization CMB temperature T cmb = K -200  K <  T < 200  K  T rms ~ 70  K  T pE ~ 5  K  T pB ~ nK

Recall Fourier series

Hence, a powerful tool for constraining cosmological parameters. Fig. M. White 1997 The Angular power spectrum of CMB anisotropy depends sensitively on Cosmological parameters Multi-parameter Joint likelihood (MCMC)

Low multipole : Sachs-Wolfe plateau Moderate multipole : Acoustic “Doppler” peaks High multipole : Damping tail Dissected CMB Angular power spectrum (fig credit: W. Hu) CMB physics is very well understood !!!

Music of the Cosmic Drum

Perturbed universe: superposition of random `pings’ (Fig: Einsentein )

Ping the ‘Cosmic drum’ More technically, the Green function (Fig: Einsentein ) 150 Mpc.

Ripples in the different constituents 150 Mpc. (Einsentein et al. 2005)

Fig:Hu & Dodelson 2002 Sensitive to curvature CMB Angular power spectrum

Fig:Hu & Dodelson 2002 Sensitive to Baryon density CMB Angular power spectrum

2003 Second NASA CMB Satellite mission First NASA CMB Satellite mission

NASA Launched July 2001 Wilkinson Microwave Anisotropy Probe NASA/WMAP science team

Covers 30% sky daily, Whole sky in 6 months WMAP CMB mission WMAP data: 7 year: Jan 26, year: Feb 6, year: Mar, year Feb, 2003 NASA : Launched July 2001

K band 23 GHz Ka band 33 GHz Q band 41 GHz V band 61 GHz W band 94 GHz CMB anisotropy signal WMAP multi-frequency maps

-200  K <  T < 200  K  T rms ~ 70  K CMB temperature T cmb = K Saha, Jain, TS 2006 WMAP map of CMB anisotropy

Independent, self contained analysis of WMAP multi-frequency maps Saha, Jain, Souradeep (WMAP1: Apj Lett 2006) WMAP3 2 nd release : TS,Saha, Jain: Irvine proc.06 Eriksen et al. ApJ WMAP: Angular power spectrum Good match to WMAP team IIT Kanpur + IUCAA

(48.3  1.2, 544  17) (48.8  0.9, 546  10) (41.7  1.0,  5.6) (41.0  0.5,  3.5) (74.1  0.3,  0.8) (74.7  0.5,  0.8 Characteristic size & amplitude of hot/cold spots in the CMB map (Saha, Jain, Souradeep Apj Lett 2006)

Flat Universe Hyperbolic Universe Spherical Universe Geometry of the Universe is FLAT

WMAP 5 & 7: Angular power spectrum 3 rd peak Fig.: Tuhin Ghosh

Current Angular power spectrum Image Credit: NASA / WMAP Science Team 3 rd peak 6 th peak 4 th peak 5 th peak

Standard cold dark matter Cosmological constant + cold dark matter Gravitational Instability ( now )(quarter size )(half size) Time  expansion  (fig: Virgo simulations)

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