Latest Results from CMB Experiments (Overview) - PowerPoint PPT Presentation

Latest Results from CMB Experiments (Overview) 小松英一郎（テキサス宇宙論センター , テキサス大学オースティン校） CMB ワークショップ 2010, 国立天文台 , 6 月 7 日

1. Temperature Anisotropy 2

揺らぎの解析： ２点相関関数 θ COBE 1989 • C( θ )=(1/4 π ) ∑ (2l+1) C l P l (cos θ ) • “ パワースペクトル ” C l – l ~ 180 度 / θ θ WMAP 2001 3

WMAP 7-year Power Spectrum Larson et al. (2010) Angular Power Spectrum Large Scale Small Scale about COBE 1 degree on the sky =180 deg/ θ 4

• WMAP (2001–2010), Space, D=1.5m, ν =23, 33, 41, 61, 94GHz • l=2–1000; Temp &Pol, 10 detectors ( HEMT ) • ACBAR (2001–2005), South Pole, D=2.1m, ν =150GHz • l=470–2600; Temp only, 16 detectors ( bolo ) • QUaD (2005–2007), South Pole, D=2.6m, ν =100, 150GHz • l=200–3000; Temp & Pol, 31 detectors ( bolo ) • ACT (2007–), Chile, D=6m, ν =148, 218, 277GHz • l=200–8000; Temp only, 3072 detectors ( bolo ) • SPT (2007–), South Pole, D=10m, ν =95, 150, 220GHz • l=2000–9000; Temp only, 960 detectors ( bolo ) 5

WMAP7 + ACBAR + QUaD Larson et al. Reichardt et al. Angular Power Spectrum Brown et al. 6 =180 deg/ θ

WMAP7 + ACBAR + QUaD Larson et al. Reichardt et al. Angular Power Spectrum Brown et al. 7 =180 deg/ θ

High-l Temperature C l : Improvement from 5-year Angular Power Spectrum 8 =180 deg/ θ

Detection of Primordial Helium Angular Power Spectrum 9 =180 deg/ θ Komatsu et al. (2010)

Effect of helium on C lTT • We measure the baryon number density, n b , from the 1st- to-2nd peak ratio. • As helium recombined at z~1800, there were fewer electrons at the decoupling epoch (z=1090): n e =(1–Y p )n b . • More helium = Fewer electrons = Longer photon mean free path 1/( σ T n e ) = Enhanced damping • Y p = 0.33 ± 0.08 (68%CL) • Consistent with the standard value from the Big Bang nucleosynthesis theory: Y P =0.24. • Planck should be able to reduce the error bar to 0.01 . 10

Another “3rd peak science”: Number of Relativistic Species N eff =4.3 ±0.9 from external data 11 from 3rd peak Komatsu et al. (2010)

Komatsu et al. (2010) And, the mass of neutrinos • WMAP data combined with the local measurement of the expansion rate (H 0 ), we get ∑ m ν <0.6 eV (95%CL) 12

WMAP7 + ACT 6000 Larson et al. WMAP 7yr Fowler et al. ACT 148 GHz 5000 Angular Power Spectrum TT /2 ! [ µ K 2 ] 4000 3000 l ( l +1)C l 2000 1000 0 10 50 100 500 1000 1500 2000 3000 13 Multipole moment l

ACT: Sneak Peek From Das et al. (2010) in preparation 10 3 10 2 10 1 10 0 1000 2000 3000 • From Szanne Staggs’ talk at Perimeter (publicly available) 14

Has the CMB lensing been detected by ACBAR? ACBAR data: Reichardt et al. (2009) blue: without lens red: with lens • The lensing effect smears the acoustic oscillation. 15

Reichardt et al. (2009) • Formal statistical significance of evidence for the Likelihood CMB lensing is 2.3 σ (WMAP5+ACBAR) • Not enough for detection. • ACT will probably detect it with high significance! 1 (Observed amplitude of lensing)/(Expected amplitude) 16

Planck: Expected C lTemperature WMAP (Simulation) Planck (Simulation) • WMAP: l~1000 => Planck: l~3000 • They will definitely detect lensing & helium, and perhaps Neff–3. 17

ACT: Sneak Peek From Das et al. (2010) in preparation 10 3 10 2 s e c r u o S t n i o P m o d n a R P r 10 1 i m a Sunyaev-Zel’dovich Effect r y C M B 10 0 1000 2000 3000 4000 5000 6000 7000 8000 • From Szanne Staggs’ talk at Perimeter (publicly available) 18

Zel’dovich & Sunyaev (1969); Sunyaev & Zel’dovich (1972) Sunyaev–Zel’dovich Effect observer • Δ T/T cmb = g ν y Hot gas with the electron temperature of T e >> T cmb y = (optical depth of gas) k B T e /(m e c 2 ) = [ σ T /(m e c 2 )] ∫ n e k B T e d(los) = [ σ T /(m e c 2 )] ∫ ( electron pressure )d(los) g ν =–2 ( ν =0); –1.91, –1.81 and –1.56 at ν =41, 61 and 94 GHz 19

“World” Power Spectrum SPT ACT Lueker et al. Fowler et al. point source point source thermal SZ thermal SZ kinetic SZ • The SPT measured the secondary anisotropy from (possibly) SZ. The power spectrum amplitude is A SZ =0.4–0.6 times the expectations. Why? 20

Lower A SZ : Two Possibilities • [1] The number of clusters is less than expected. • In cosmology, this is parameterized by the so-called “ σ 8 ” parameter. x [gas pressure] 2 • σ 8 is 0.77 (rather than 0.81): ∑ m ν ~0.2eV? 21

Lower A SZ : Two Possibilities • [2] Gas pressure per cluster is less than expected. • The power spectrum is [gas pressure] 2 . • A SZ =0.4–0.6 means that the gas pressure is less than expected by ~0.6–0.7. • We can test this by looking at the SZ effect of the individual clusters! 22

WMAP 7-year Measurements! 23 (Komatsu et al. 2010)

Low-SZ is seen in the WMAP X-ray Data Model d: ALL of “cooling flow clusters” are relaxed clusters. e: ALL of “non-cooling flow clusters” are non-relaxed clusters. 24

Low-SZ: Signature of mergers? X-ray Data Model d: ALL of “cooling flow clusters” are relaxed clusters. e: ALL of “non-cooling flow clusters” are non-relaxed clusters. 25

Recap: Temperature C l • 6 acoustic peaks (up to l=2000) have been measured. • Baryon density, dark matter density, helium abundance, and N eff have been constrained. • The primordial tilt: n s =0.967 ±0.013 (68%CL) • Detection of lensing is yet to be made. (ACT, Planck) • Missing SZ: the next frontier? 26

2. CMB Polarization 27

CMB Polarization • CMB is (very weakly) polarized! 28

Physics of CMB Polarization Wayne Hu • CMB Polarization is created by a local temperature quadrupole anisotropy. 29

Principle North Hot Cold Cold Hot East • Polarization direction is parallel to “hot.” 30

CMB Polarization on Large Angular Scales (>2 deg) Matter Density Potential Δ T/T = (Newton’s Gravitation Potential)/3 Δ T Polarization • How does the photon-baryon plasma move? 31

CMB Polarization Tells Us How Plasma Moves at z=1090 Zaldarriaga & Harari (1995) Matter Density Potential Δ T/T = (Newton’s Gravitation Potential)/3 Δ T Polarization • Plasma falling into the gravitational potential well = Radial polarization pattern 32

Quadrupole From Velocity Gradient (Large Scale) Sachs-Wolfe: Δ T/T= Φ /3 Δ T Stuff flowing in Potential Φ Acceleration a =– ∂Φ a >0 =0 Velocity Velocity gradient Velocity in the rest The left electron sees colder e – e – frame of electron photons along the plane wave Polarization Radial None 33

Quadrupole From Velocity Gradient (Small Scale) Compression increases Δ T temperature Stuff flowing in Potential Φ Acceleration Pressure gradient slows a =– ∂Φ – ∂ P down the flow a >0 <0 Velocity Velocity gradient Velocity in the rest e – e – frame of electron Polarization Radial Tangential 34

Komatsu et al. (2010) Two-dimensional View • Expected polarization pattern around cold and hot spots have been detected! • The overall significance level: 8 σ • This is the so-called “E-mode” polarization. 35

E-mode and B-mode • Gravitational potential can generate the E- mode polarization, but not B-modes. • Gravitational waves can generate both E- and B-modes! E mode B mode 36

WMAP 7-year TE Correlation [21 σ ] Angular Power Spectrum radial around cold tangential around cold 37 Larson et al. (2010)

No TB Correlation + = 0 Angular Power Spectrum 38 Larson et al. (2010)

E-mode Potential Φ ( k , x )=cos( kx ) Direction of a plane wave Polarization Direction • E-mode : the polarization directions are either parallel or tangential to the direction of the plane wave perturbation. 39

B-mode G.W. h( k , x )=cos( kx ) Direction of a plane wave Polarization Direction • B-mode : the polarization directions are tilted by 45 degrees relative to the direction of the plane wave perturbation. 40

Gravitational Waves and Quadrupole •Gravitational waves stretch space with a quadrupole pattern. “ + mode” 41 “X mode”

Quadrupole from G.W. Direction of the plane wave of G.W. h( k , x )=cos( kx ) h X temperature polarization B-mode • B-mode polarization generated by h X 42

Quadrupole from G.W. Direction of the plane wave of G.W. h( k , x )=cos( kx ) h + temperature polarization E-mode • E-mode polarization generated by h + 43

Polarization Power Spectrum Larson et al. Brown et al. Chiang et al. • No detection of B-mode polarization yet. B-mode is the next holy grail! 44

BICEP (2006–) • D= 25cm , ν =100 & 150GHz • 49 detectors ( bolometer ) • Refracting telescope, with the optical system put in a cryostat (250mK). • A good design, solely focused on detecting the primordial 45 gravitational waves. The B-mode only limit is r<0.72 (Chiang et al.)

WMAP’s polarization data-only limits on tensor-to-scalar ration • BB : r<2.1 • EE/BB : r<1.6 • TE/EE/BB : r<0.93 • TT/TE/EE/BB : r<0.36 46 Komatsu et al. (2010)