Leptons, Photons & the CMB Ned Wright, UCLA 16 Aug 2007

Nobel Prize in Physics 2006 John Mather for the CMB Spectrum George Smoot for the CMB anisotropy

COBE View of the CMB Sky

Two Fluids in the Early Universe Most of the mass is dark matter –80-90% of the density –Zero pressure –Sound speed is zero The baryon-photon fluid –baryons are protons & neutrons = all ordinary matter –energy density of the photons is bigger than c 2 times the mass density of baryons –Pressure of photons = u/3 = (1/3)  c 2 –Sound speed is about c/  3 = 170,000 km/sec

“Normal” vs Conformal ST Diagram Constant SE course is a curve on the globe but a straight line on the conformal Mercator map. Constant speed-of-light is a curve on the “normal” space-time diagram but a straight line on the conformal diagram.

Traveling Sound Wave: c s = c/  3

Stay at home Dark Matter

Interference at last scattering For the wavelength illustrated [1/2 period between the Big Bang and recombination], the denser = hotter effect and potential well = cooler effect have gotten in phase. For larger wavelengths they are still out of phase at recombination.

Many parameters to measure Careful measurements of the power at various angular scales can determine the Hubble constant, the matter density, the baryon density, and the vacuum density.

COBE View was Blurry

A New Cosmology Satellite

Combination to remove foreground

QVW as RGB

Effects on Peak Position: l pk +Open or vacuum dominated Universes give larger distance to last scattering surface +High matter density gives smaller wavelength

The CMB does not imply flatness But CMB + H o (or other data) do imply flatness.

 CDM is a Good Fit

So is “super Sandage”

Info from peak & trough heights Overall Amplitude of the perturbations –Agrees with large scale structure if almost all the dark matter is COLD dark matter Primordial power spectrum power law spectral index: n = ± without running index. –EPAS inflationary prediction is n = 1 Baryon/photon and DM/baryon density ratios –  b = 0.42 yoctograms/m 3 = 0.42  gm/cc –  cdm = 1.9 yg/m 3 [  ≡  h 2 =  /{18.8 yg/m 3 }]

Baryon & CDM densities BBNS value 5:1 Ratio

 m h 2 is known from the CMB CMB peak heights give the actual matter density: 2.5 yoctograms per cubic meter to 8% precision. –This assumes 3 neutrino types. Ratio of matter density to relativistic density at last scattering is measured. This means that a given  m corresponds to a given H o. The HST key project value of 72  8 km/sec says  m is close to 0.24 but with 25% precision from the 11% uncertainty in H o. Values of  =  m h derived from large scale structure studies are consistent with the HST Key Project Hubble constant.

For pc = 3kT, limits on mass Mass 0.5 meV is relativistic now, but higher masses go slower and don’t travel as far. For m > 550 eV, distance << clustering length.

From astro- ph/ Slight preference for 700 eV mass, and anything with m > 2 keV is in the CDM limit Based on WMAP 1 st year results. Warm Dark Matter eliminates the excess of low-mass halos. Density is very sub- thermal but could be a sterile neutrino.

Active Neutrinos Active neutrinos must have masses so small that they free-stream out of structures. Limit on masses based only on the hot fraction of the dark matter.

The End of Inflation Pure H-Z: n=1, R=0 now fails  4 still fails, m 2  2 is OK.

The Three Simplicities  = 0 but this probably is not correct.  tot = 1: a flat Universe. w = -1 if there is dark energy. –Note that if w = -1, the dark energy is Lorentz invariant, but if w ≠ -1 observers can measure their velocity with respect to the dark energy so the dark energy has to be a dynamical thing that will react to inhomogeneities in the Universe. Thus  DE and w will be functions of space and time.

We should prove flatness. The success of the flat model with w = -1 can not be used to justify assuming flatness when trying to find w and w’. Certainly  tot = 1 is simpler, but –  X = 0 is simpler, no CDM is simpler & w = -1 is simpler But the model consistent with both the CMB and SNe data moves as w is varied, and is most consistent with the Hubble constant from the HST Key Project when w is close to -1. So w can be measured using all data combined but be suspicious of priors on  tot or  M.

Can we say anything about w? Pretty good mutual agreement of 4 datasets for w = -1 and  tot =1. This agreement is slowly lost as w moves away from -1.

WMAP plus LSS and BAO The only limit on w worth noting.

Compare to A little flatter, less “phantom” support.

Late ISW Effect: Another test for  Potential only changes if  m  1 (or in non-linear collapse, but that’s another story [Rees-Sciama effect]).

Potential decays at z  0.6

CMB-LSS correlation seen by WMAP This late ISW effect occurs on our past light cone so the  T we see is due to structures we also see. Correlation between WMAP and LSS seen by: –Boughn & Crittenden (astro-ph/ ) at 2.75  with hard X-ray background and 2.25  with NVSS –Nolta et al. (astro-ph/ ) at 2  with NVSS –Afshordi et al (astro-ph/ ) at 2.5  with 2MASS

2MASS galaxies reach z = 0.1 Credit: Tom Jarrett, IPAC

W IDE-FIELD I NFRARED S URVEY E XPLORER I am the PI on a MIDEX called WISE, an all-sky survey in 4 bands from 3.3 to 23  m. WISE will find and study the closest stars to the Sun, the most luminous galaxies in the Universe, and also map the large- scale structure out to redshift z=1, covering the era when the late ISW effect should be generated. WISE is under construction now and scheduled to fly in late 2009.

Current Conclusions Ratio of CMB amplitude to galaxy clustering amplitude constrain the typical relict speed of the dark matter to be slower than a 550 eV thermal neutrino. Also constrain the fraction of the dark matter that is traveling much faster: limits the sum of active neutrino masses to < 1 eV. Peak:trough:peak ratios determine the dark matter density: 2 yoctograms/m 3. Dark energy has < w < -0.8: a boring cosmological constant?

Future Prospects WMAP is entering its 7th year of data taking. Planck will launch in late –Much better angular resolution and sensitivity –Higher frequency channels –Better knowledge of galactic dust foregrounds –Improved matter and baryon densities –Improved spectral index and curvature of the primordial power spectrum –Thermal Sunyaev-Zeldovich data on thousands of clusters

Papers to view: Jeong & Smoot (ABS-S S10-127; astro-ph/ ): a search for Cosmic Strings in the CMB map. Similar to Lo & Wright (astro-ph/ ) but using 3 year data. None seen to date, but Planck will greatly improve this search. Hayashi etal, (ABS-S S10-108; astro-ph/ ): inflation model consistent with the WMAP n = ± 0.017