TheThe CosmicCosmic MicrowaveMicrowave BackgroundBackground Past,Past, PresentPresent andand FutureFuture Martin White University of California, Berkeley Lawrence Berkeley National Laboratory The CMB C2CR07 • Feb 2007 1 Outline A brief history of cosmology from the cosmic microwave background. – Penzias & Wilson – COBE The current state-of-the-art and what we have learnt. – WMAP3 The near future. – Planck Possible future missions. – Secondary anisotropies, low-z structure – Polarization - the next frontier The CMB White 2 C2CR07 • Feb 2007 2 In the beginning was Bell Labs Penzias and Wilson shared half of the 1978 Nobel Prize for the discovery of the cosmic microwave background (CMB) radiation. Fluctuations are black-body, isotropic and not correlated with any (local) structure in the Universe. The CMB White 3 C2CR07 • Feb 2007 3 …then there was COBE … Nobel prize in Physics, 2006, awarded to Mather and Smoot “for their discovery of the blackbody form and anisotropy of the cosmic microwave background radiation” The CMB White 4 C2CR07 • Feb 2007 4 A revolution in our understanding of the Universe Existence of CMB – One of the pillars of the hot big-bang model. Measurement of the black-body spectrum – T = 2.725 ± 0.001 K, deviations < 10-4 – Sets the temperature scale of the Universe Only cosmological parameter known to better than 1%! – Rules out significant energy injection below z~107. Measurement of the anisotropy – Shrunk substantially the range of viable cosmological models. – Gravitational instability in a dark matter dominated Universe formed large-scale structure seen by e.g. 2dF or SDSS. – The fluctuations are of the form predicted by inflation. – The large-scale structure of space-time is “simple”. Precise normalization of large-scale structure. All right. But apart from the sanitation, the medicine, education, wine, public order, irrigation, roads, the fresh water system, and public health . What have the Romans ever done for us? Reg, spokesman for the People’s Front of Judea The CMB White 5 C2CR07 • Feb 2007 5 2003: WMAP reported 1st year data! This … Became this! Power Angular scale From lambda.gsfc.nasa.gov The CMB White 6 C2CR07 • Feb 2007 6 Current state-of-the-art From lambda.gsfc.nasa.gov The CMB White 7 C2CR07 • Feb 2007 7 Of the “dozen” parameters in our cosmological model: 1 parameter known to better than 1% (2 if you count peak angular scale) 5 parameters known to better than 10% (independently) from the CMB alone. The CMB White 8 C2CR07 • Feb 2007 8 Cosmological parameters 2 ωm= Ωmh = 0.1277 ± 0.008 -30 3 . ρm= (2.11 ± 0.13) x 10 g/cm 2 ωb= Ωbh = 0.02229 ± 0.0007 -31 3 . ρb= (4.19 ± 0.13) x 10 g/cm δΦ/c2 = (3 ± 0.1) x 10-5 o θA = 0.5952 ± 0.0021 s = (147.8 ± 2.6) Mpc = (4.56 ± 0.08) x 1026 cm 28 dLS = (14.2 ± 0.2) Gpc = (4.38 ± 0.08) x 10 cm The CMB White 9 C2CR07 • Feb 2007 9 Other inferences From the narrow first peak we know that whatever “rang the bell” was sharp and of short duration, not a continuous driving. The fluctuations are dominated by large-scale density perturbations (not vorticity modes or gravity waves). The universe was not “weird” at z~103. Inflation is in good shape. – Fluctuations are small, harmonic, Gaussian & adiabatic – Limits on specific models of inflation – e.g. λφ4 inflation is ruled out at ~ 2-3σ . – Tentative detection of departure from scale-invariance (maybe!). ns=0.958 ± 0.016 (no running; lambda.gsfc.nasa.gov) ns=0.970 ± 0.016 (no running; Huffenberger et al. 2007) ns=0.993 ± 0.030 (no running+r; Cortes, Liddle & Mukherjee 2007) ns=0.981 ± 0.034 (w/ running+r; Cortes, Liddle & Mukherjee 2007) See Erikson et al. (2007); Huffenberger et al. (2007) for revisions to the initially published WMAP ns results. The CMB White 10 C2CR07 • Feb 2007 10 Polarization In the presence of anisotropy we expect scattering to generate (linear) polarization. Consequence of electro-magnetic gauge invariance! Polarization provides a prediction, a cross-check and further information about conditions at last-scattering and reionization. Rees (1968) Kaiser (1983) Hu & White (1997) The CMB White 11 C2CR07 • Feb 2007 11 E- and B-modes Polarization is made up of two “modes”, referred to as E- and B- modes because of their global parity properties. E-modes B-modes Note that E-modes have no handedness, whereas B-modes do and thus cannot be generated by scalar (density) perturbations. The CMB White 12 C2CR07 • Feb 2007 12 Polarization: first detection by DASI Single shaped l-bin Five l-bins 100 6.3σ ) 50 E detection 2 K µ consistent ( 0 with theory. E -50 ) Consistent 2 50 K B µ with zero ( 0 (theory) B -50 ) 100 2.9σ 2 Leitch et al., 2005 K µ TE detection ( 0 consistent -100TE with theory 0 200 400 600 800 1000 l (angular scale) The CMB White 13 C2CR07 • Feb 2007 13 The world compilation Courtesy Lewis Hyatt Multipole The CMB White 14 C2CR07 • Feb 2007 14 The picture from WMAP3 Temperature Adiabatic / inflationary peak Polarization from z~103 Polarization from z~10 Page et al. 2006 Polarization from GWs from z~10?? (Not seen! Upper limit.) The CMB White 15 C2CR07 • Feb 2007 15 The near (!) future: Planck Planck is part of ESA’s “Cosmic Visions” program and is currently scheduled for launch in July 2008 along with the Herschel satellite. Planck will be the first sub-mm mission to map the entire sky with mJy sensitivity with resolution better than 10 arcminutes. The science enabled by such a mission spans many areas of astrophysics and cosmology. K) µ Brightness temperature ( 10 Frequency (GHz) 1000 The CMB White 16 C2CR07 • Feb 2007 16 Planck in cartoons The CMB White 17 C2CR07 • Feb 2007 17 Planck being assembled The CMB White 18 C2CR07 • Feb 2007 18 Real hardware!! Final assembly of the Planck satellite and payload in Europe is almost complete. The CMB White 19 C2CR07 • Feb 2007 19 The orbit Planck will make its measurements from the Earth-Sun L2 point. It makes a map of the full sky every 6 months. The CMB White 20 C2CR07 • Feb 2007 20 A full sky map of temperature and polarization The CMB White 21 C2CR07 • Feb 2007 21 What (we expect) Planck will add In addition to wider frequency coverage and better sensitivity than WMAP, Planck has the resolution needed to see into the damping tail. It will be the first experiment to make a cosmic variance limited measurement of the scales around the 3rd and 4th peaks. (4yr) (1yr) The CMB White 22 C2CR07 • Feb 2007 22 What (we hope) Planck will add A precise measurement of the E-mode polarization power spectrum and a highly sensitive search for B-modes (from inflation?). The CMB White 23 C2CR07 • Feb 2007 23 A dramatic advance Planck will essentially clean up the primary temperature anisotropies and make great inroads on polarization. Many of the most important book cosmological parameters will blue be known much better after Planck flies. Planck Projected WMAP likelihood Projected Planck likelihood on Hubble constant The CMB White 24 C2CR07 • Feb 2007 24 CMB science An inroad to inflation – COBE defined the amplitude of the fluctuations: δ ~10-5 – To constrain models need to measure ns and running Expect δns~0.03 → 0.007 and δα~0.04 → 0.003 – c.f. WMAP: longer level arm, more spectra – Also break (accidental n-τ) degeneracy with EE – May be the first measurement of ns<1 – Rule out [?] isocurvature contribution, P(k) features … – Find GW signal [?] and constrain the energy scale of inflation. 2 – Non-Gaussianity (limits on fNL~100 drop to fNL~1: δtot~δlin+fNLδlin ) Constraining dark energy, Ωm, h, etc. – CMB gives: ωm, ωb, θA. Improve constraints by 5-10. – Currently δD(z=1100) ~ 3% limited by ωm (δωm~ 6%) – Planck should get δωm~ 0.9%. – In principle δD(z=1100) ~ 0.2%! Secondary Anisotropies – Highly significant detection of gravitational lensing – Constraints on how the Universe reionized (large & small scales) – Catalog of the most massive clusters of galaxies, anywhere in the Universe – Cross-correlation for the clustering of dark energy, massive neutrinos, … The CMB White 25 C2CR07 • Feb 2007 25 The CMB “prior” With WMAP, and certainly after Planck, we will have very precise knowledge of the universe at z~1000. We will have tightly constrained the physical densities of matter and baryons, the amplitude of the fluctuations in the linear phase over 3 decades in length scale and the shape of the primordial power spectrum. Our knowledge of physical conditions and large-scale structure at z~103 will be better than our knowledge of such quantities at z~0! If dark energy is a recent phenomenon, then we can translate this knowledge reliably to intermediate redshifts which are currently at the observational frontier. The CMB White 26 C2CR07 • Feb 2007 26 The real-space z~3 power spectrum CMB enables us to constrain the high-z matter power spectrum (with lengths measured in meters!) Example: using the WMAP 3yr data constrains Δ2(k) to 7% 7% measurement near near k~0.01/Mpc acoustic peak scale. assuming a basic ΛCDM model. This drops to 3% if τ is controlled for. With Planck this will White ‘06 be a percent level measurement! The CMB White 27 C2CR07 • Feb 2007 27 Making it to z=0 The uncertainty in large-scale structure formation thus comes from the extrapolation to z=0 and to redshift space. – Growth of fluctuations between z~3 and z=0 depends on dark energy and massive neutrinos (vertical shifts).