Wilkinson Microwave Anisotropy Probe (WMAP) Observations: The Final Results

Transcription

1 WMAP Wilkinson Microwave Anisotropy Probe (WMAP) Observations: The Final Results Eiichiro Komatsu (Max-Planck-Institut für Astrophysik) HEP-GR Colloquium, DAMTP, Cambridge, January 30,

2 used to be WMAP at Lagrange 2 (L2) Point June 2001: WMAP launched! February 2003: The first-year data release March 2006: The three-year data release March 2008: The five-year data release January 2010: The seven-year data release September 8, 2010: WMAP left L2 December 21, 2012: The final, nine-year data release 2

3 Why am I here? Why should HEP/GR people care about temperature and polarization maps of the sky measured in microwave bands? Because: 1. They tell us something about inflation in very high energy scale 2. They constrain physics beyond the SM: e.g., the effective number of relativistic degrees of freedom 3

4 9-year Science Highlights 1. Single-field slow-roll inflation continues to be supported by the data, with much restricted range of the parameter space 2. The joint constraint on the helium abundance and the number of relativistic species from CMB strongly supports Big Bang nucleosynthesis 4

5 WMAP9 +ACT+SPT WMAP9 +ACT+SPT +BAO+H0 5

6 Bispectrum Results k1 k3 fnl local = 37±20 (68% CL) k2 after subtracting off the low-redshift ISW-lensing bias of ΔfNL local =2.6 fnl equilateral = 51±136 (68% CL) fnl orthogonal = 245±100 (68% CL) more later! 6 We do not claim detection of any forms of non-gaussianity

7 Effective Number of Relativistic Degrees of Freedom at z~1090 BBN prediction WMAP9 +ACT+SPT +BAO+H0 WMAP9 +ACT+SPT Helium Abundance by Mass Fraction 2 7

8 WMAP Science Team C.L. Bennett M.R. Greason J. L.Weiland K.M. Smith G. Hinshaw M. Halpern E.Wollack C. Barnes N. Jarosik R.S. Hill J. Dunkley R. Bean S.S. Meyer A. Kogut B. Gold O. Dore L. Page M. Limon E. Komatsu H.V. Peiris D.N. Spergel N. Odegard D. Larson L. Verde E.L. Wright G.S. Tucker M.R. Nolta 8

9 WMAP 9-Year Papers Bennett et al., Final Maps and Results, submitted to ApJS, arxiv: Hinshaw et al., Cosmological Parameter Results, submitted to ApJS, arxiv:

10 From Cosmic Voyage

11 CMB: The Farthest and Oldest Light That We Can Ever Hope To Observe Directly When the Universe was 3000K (~380,000 years after the Big Bang), electrons and protons were combined to form neutral hydrogen. 11

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13 Analysis: θ 2-point Correlation C(θ)=(1/4π) (2l+1)ClPl(cosθ) How are temperatures on two COBE points on the sky, separated by θ, are correlated? Power Spectrum, Cl How much fluctuation power do we have at a given angular scale? l~180 degrees / θ WMAP 13

14 COBE/DMR Power Spectrum Angle ~ 180 deg / l ~90 deg ~9 deg (quadrupole) Angular Wavenumber, l 14

15 COBE To WMAP θ COBE is unable to resolve the structures below ~7 degrees COBE WMAP s resolving power is 35 times better than COBE. θ What did WMAP see? WMAP 15

16 WMAP 9-year Power Spectrum Angular Power Spectrum Large Scale COBE about 1 degree on the sky Small Scale 16

17 The Cosmic Sound Wave The Universe as a Miso soup Main Ingredients: protons, helium nuclei, electrons, photons We measure the composition of the Universe by analyzing the wave form of the cosmic sound waves. 17

18 9-year temperature Cl 18

19 7-year temperature Cl 19

20 What changed? An improved analysis! The error bar decreased by more than expected for the number of years (9 vs 7). Why? We now use the optimal (minimum variance) estimator of the angular power spectrum. Previously, we estimated Cl for low-l (l<600) and high-l (l>600) separately. No weighting for low-l and inverse-noise-weighting for high-l. This results in a sub-optimal estimator near l~600. We now use the optimal (S+N) 1 weighting. 20

21 Variance (sub-optimal) / Variance (optimal) 21

22 9-year (sub-optimal) vs 9-year (optimal) 22

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24 Adding the small-scale CMB data Atacama Cosmology Telescope (ACT) a 6-m telescope in Chile, led by Lyman Page (Princeton) Cl from Das et al. (2011) South Pole Telescope (SPT) a 10-m telescope in South Pole, led by John Carlstrom (Chicago) Cl from Keisler et al. (2011); Reichardt et al. (2012) These data are not the latest [Story et al. (2012) for SPT; Das et al. (2013) for ACT] 24

25 South Pole Telescope (SPT) 1000 Atacama Cosmology Telescope (ACT)

26 Adding the small-scale CMB tends to prefer a lower power at high multipoles than predicted by the WMAP-only fit (~1σ lower) 26

27 The number of neutrino species total radiation density: photon density: neutrino density: where neutrino+extra species: 27

28 What the extra radiation species does Extra energy density increases the expansion rate at the decoupling epoch. Smaller sound horizon: peak shifts to the high l Large damping-scale-to-sound-horizon ratio, causing more Silk damping at high l Massless free-streaming particles have anisotropic stress, affecting modes which entered the horizon during radiation era. 28

29 Neutrinos have anisotropic stress This changes metric perturbations as tr(i-j) 0-0 This changes the early Integrated-Sachs-Wolfe effect (ISW) 29

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35 Effect of helium on Cl TT We measure the baryon number density, nb, from the 1stto-2nd peak ratio. For a given nb, we can calculate the number density of electrons: ne=(1 Yp/2)nb. As helium recombined at z~1800, there were even fewer electrons at the decoupling epoch (z=1090): ne=(1 Yp)nb. More helium = Fewer electrons = Longer photon mean free path 1/(σTne) = Enhanced Silk damping 35

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38 Effective Number of Relativistic Degrees of Freedom at z~1090 BBN prediction WMAP9 +ACT+SPT +BAO+H0 WMAP9 +ACT+SPT Helium Abundance by Mass Fraction Simultaneous Fit to Helium and Neff Results consistent with the BBN prediction 38

39 Implications for Inflation Two-point function analysis: the tensor-to-scalar ratio, r, and the primordial spectral tilt, ns Three-point function analysis: are fluctuations consistent with Gaussian? 39

40 WMAP 9-year Power Spectrum Angular Power Spectrum Large Scale COBE about 1 degree on the sky Small Scale 40

41 Getting rid of the Sound Waves Large Scale Small Scale Angular Power Spectrum Primordial Ripples 41

42 The Early Universe Could Have Done This Instead Large Scale Small Scale Angular Power Spectrum More Power on Large Scales 42

43 ...or, This. Large Scale Small Scale Angular Power Spectrum More Power on Small Scales 43

44 ...or, This. Large Scale Small Scale Angular Power Spectrum Parametrization: l(l+1)cl ~ l ns 1 And, inflation predicts ns~1 44

45 Gravitational waves are coming toward you... What do you do? Gravitational waves stretch space, causing particles to move. 45

46 Two Polarization States of GW This is great - this will automatically generate quadrupolar anisotropy! 46

47 From GW to CMB Anisotropy 47

48 From GW to CMB Anisotropy Redshift Redshift Blueshift Blueshift Redshift Blueshift Blueshift Redshift 48

49 Tensor-to-scalar Ratio, r r = [Power in Gravitational Waves] / [Power in Gravitational Potential] Theory of Cosmic Inflation predicts r <~ 1 I will come back to this in a moment 49

50 WMAP9 +ACT+SPT WMAP9 +ACT+SPT +BAO+H0 50

51 What do BAO and H0 do? BAO and H0 both measure distances in a low-z universe. This helps determine the matter density independent of ns. (In the temperature power spectrum, there is a mild correlation between them.) 51

52 R 2 Inflation [Starobinsky 1980] This theory is conformally equivalent to a theory with a canonically normalized scalar field with a potential given by where [very flat potential for large Ψ > smaller r] 52

53 Bispectrum k1 k3 Three-point function! k2 Bζ(k1,k2,k3) = <ζk1ζk2ζk3> = (amplitude) x (2π) 3 δ(k1+k2+k3)f(k1,k2,k3) model-dependent function Primordial fluctuation fnl 53

54 MOST IMPORTANT

55 Probing Inflation (3-point Function) Inflation models predict that primordial fluctuations are very close to Gaussian. In fact, ALL SINGLE-FIELD models predict a particular form of 3-point function to have the amplitude of fnl=0.02. Detection of fnl>1 would rule out ALL single-field models! No detection of 3-point functions of primordial curvature perturbations. The 68% CL limit is: fnl = 37 ± 20 (1σ) The WMAP data are consistent with the prediction of simple single-field inflation models: 1 ns r fnl 55

56 Komatsu&Spergel (2001) 56

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58 fnl equilateral = 51±136 (68% CL) no evidence whatsoever FIELD INTERACTION 58

59 Orthogonal Shape It s a tricky shape: negative in the folded limit; positive in the equilateral limit 59

60 Orthogonal Shape It s a tricky shape: negative in the folded limit; positive in the equilateral limit fnl orthogonal = 245±100 (68% CL) Statistically, it is a 2.45σ result. Don t jump: we do not claim that this is a detection, while this is an intriguing result. Now, look at the null tests. 60

61 A long story short: A channel-to-channel consistency test is a little bit worrying, but we did not find an obvious systematics which can make this signal go away. Wait for Planck! 61

62 Statistical Anisotropy Is the power spectrum anisotropic? P(k) = P( k )[1+g*(cosθ) 2 ] This makes shapes of temperature spots anisotropic on the sky. Statistically significant detection of g* Is this cosmological? The answer is no: the same (identical!) effect can be caused by ellipticity of beams 62

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64 This is coupled with the scan pattern WMAP scans the ecliptic poles many more times and from different orientations. Thus, the averaged beam is nearly circular in the poles. The ecliptic plane is scanned less frequently and from limited orientations. Thus, the averaged beam is more elliptical in the plane. This is exactly what the anisotropic power spectrum gives. 64

65 Creating a map with a circular beam We create a map in which the elliptical beam shape is deconvolved. The resulting map has an effective circular beam. This map is not used for cosmology, but used for the analysis of foregrounds and statistical anisotropy. 65

66 Normal Map Normal Map Residuals A deconvolved image of a supernova remnant Tau A at 23 GHz 0 mk 100 Beam Sym. Map -5 mk 5 Beam Sym. Map Residuals Deconvolved image is more circular, as expected Deconvolved map does not show the anisotropic power spectrum anymore! 0 mk mk 5 66

67 Summary The minimal, 6-parameter ΛCDM model continues to describe all the data we have No significant deviation from the minimal model Rather stringent constraints on inflation models Strong support for Big Bang nucleosynthesis with the standard effective number of neutrino species Anisotropic power spectrum is due to elliptical beams... a (Hinshaw et al. 2012) 67

68 Trispectrum Tζ(k1,k2,k3,k4)=(2π) 3 δ(k1+k2+k3+k4) {gnl[(54/25)pζ(k1)pζ(k2)pζ(k3)+cyc.] +τnl[pζ(k1)pζ(k2)(pζ( k1+k3 )+Pζ( k1+k4 ))+cyc.]} The consistency relation, τnl (6/5)(fNL) 2, may not be respected additional test of multi-field inflation! k3 k2 k3 k2 k4 k1 k4 k1 gnl τnl 68

69 The 4-point vs 3-point diagram ln(τnl) 3.3x10 4 (Smidt et al. 2010) The current limits from WMAP 9-year are consistent with single-field or multifield models. So, let s play around with the future. 77 ln(fnl) 69

70 Case A: Single-field Happiness ln(τnl) No detection of anything after Planck. Single-field survived the test (for the moment: the future galaxy 600 surveys can improve the limits by a factor of ten). 10 ln(fnl) 70

71 Case B: Multi-field Happiness ln(τnl) fnl is detected. Singlefield is dead. But, τnl is also detected, in accordance with the Suyama-Yamaguchi inequality, as expected 600 from most (if not all - 30 ln(fnl) left unproven) of multifield models. 71

72 Case C: Madness ln(τnl) fnl is detected. Singlefield is dead. But, τnl is not detected, inconsistent with the Suyama- Yamaguchi inequality. 600 (With the caveat that this may not be 30 ln(fnl) completely general) BOTH the single-field and multi-field are gone. 72