Cosmology : Cosmic Microwave Background & Large scale structure

1. Cosmology : Cosmic Microwave Background & Large scale structure • Lec. 2: • Cosmic Content • Perturbed Universe Cosmology IUCAA VSP program (May 18-22, 2012) Tarun Souradeep I.U.C.A.A.

2. Simple… yet, an exoticuniverse • 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

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

4. Matter budget of the Universe w=0 (w<-1/3) Decelerated Expansion (Non-Clustering) w=0 Decelerated Expansion (Grav. Clustering) Fig:NASA/WMAP science team

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

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

7. Dark matter in Galaxies ! R

8. Rotation of Spiral Galaxies !!!

9. Dark matter in our own backyard !?!

10. Dark matter in the Milky way

11. Dark matter in other galaxies too !!

12. Dark matter in clusters !?!

13. Hot gas in clusters Coma cluster

14. Hot gas in clusters Virgo cluster

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

16. Gravitational lensing Distant galaxies beyond a cluster are lensed….

18. Bullet cluster

19. Bullet cluster movie

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

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

22. Geometry, Expansion & Matter Dark energy causes accelerated expansion

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

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

25. Supernova in a galaxy: standard candle

26. Supernova can be seen in distant galaxies

27. Supernova in a very distant galaxy

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

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

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

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

33. Nobel Prize 2006 First detection of CMB anisotropy (1992) Cosmic Background Explorer COBE George Smoot John Mather

34. CMB Anisotropy & Polarization CMB temperature Tcmb = 2.725 K -200  K <  T < 200  K  Trms~ 70 K • TpE~ 5  K • TpB ~ 10-100 nK • Temperature anisotropy T + two polarization modes E&B • Four CMB spectra : ClTT, ClEE,ClBB,ClTE

35. Cosmic Microwave Background Anisotropy Recall Fourier series

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

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

38. Music of the Cosmic Drum

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

40. 150 Mpc. Ping the ‘Cosmic drum’ More technically, the Green function (Fig: Einsentein )

41. 150 Mpc. Ripples in the different constituents (Einsentein et al. 2005)

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

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

44. First NASA CMB Satellite mission Second NASA CMB Satellite mission 2003

45. CMB space mission : WMAP Wilkinson Microwave Anisotropy Probe NASA Launched July 2001 NASA/WMAP science team

46. WMAP CMB mission NASA : Launched July 2001 Covers 30% sky daily, Whole sky in 6 months WMAP data: 7 year: Jan 26, 2010 5 year: Feb 6, 2008 3 year: Mar, 2006 1-year Feb, 2003

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

48. WMAP map of CMB anisotropy Saha, Jain, TS 2006 CMB temperature Tcmb = 2.725 K -200  K <  T < 200  K  Trms~ 70 K

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

50. (74.10.3, 219.80.8) (74.7 0.5, 220.1 0.8 (48.3 1.2, 544 17) (48.8 0.9, 546 10) (41.7 1.0, 419.2 5.6) (41.0  0.5, 411.7 3.5) Characteristic size & amplitude of hot/cold spots in the CMB map (Saha, Jain, Souradeep Apj Lett 2006)