Cosmology from the small-scale CMB Jo Dunkley Oxford Astrophysics DESY, Sept 27 2011 The Cosmic Microwave Background • Initial fluctuations evolve, set up acoustic oscillations. • Temperature fluctuations at z~1100 sourced by density and velocity perturbations. • Affected by contents and primordial power spectrum From Wayne Hu WMAP view of sky WMAP 7-year Larson et al 2011: provided strong constraints on 6-parameter LCDM model ACT and SPT probe smaller scales Sudeep Das for the ACT collaboration Atacama Cosmology Telescope • Univ of British Columbia (Canada) • Univ of Oxford (UK: Dunkley, • Univ of Cape Town (S Africa) Addison, Hlozek) • Cardiff University (UK) • Univ of Pennsylvania (USA) • Columbia University (USA) • *Princeton University (USA) (PI L. • Haverford College (USA) Page) • INAOE (Mexico) • Univ of Pittsburgh (USA) • Univ of Kwa-Zulu Natal (S Africa) • Pontifica Universidad Catolica (Chile) • Univ of Massachusetts (USA) • Rutgers University (USA) • NASA/GSFC (USA) • Univ of Toronto (Canada) • NIST (USA) • Rome La Sapienza, MPI, Miami, Stanford, Berkeley (Das), Chicago, CfA, LLNL, IPMU Tokyo ~ 90 collaborators Measuring small scales with ACT 5200 meter elevation, one of driest places on planet 1º field of view, 6-meter dish, arcminute resolution 3 frequencies: 150-300 GHz, 3000 TES detectors How ACT/SPT compare to WMAP 1 2 3 4 Region mapped 4x with ¼ of data: Small-scale spectrum: early 2010 Fowler et al 2010: See Silk damping of primordial CMB, and then at smaller scales extra signals from galaxies and galaxy clusters. Small-scale spectrum: summer 2011 Seven or more acoustic peaks Dunkley et al. 2011 Inflation: limits from spectrum • All predictions so far consistent with CMB. Big goal: is index <1? The spectral index is still 3 sigma away. Latest from WMAP + SPT: ns = 0.966 ± 0.011 • Running index, find dns/dlnk = -0.024 ± 0.015 (ACT+WMAP+BAO+H0, similar with SPT) • New upper limit on tensors, find r < 0.19 (95% CL, ACT+WMAP+BAO+H0) r < 0.25 Dunkley et al. 2011 Primordial spectrum: no features Hlozek, JD et al. 2011 Early universe physics 7 4 4 / 3 ρrel = Neff ρ γ 8 11 Dunkley et al. 2011 Neutrinos: More species, longer radiation domination, changes equality redshift. Also - suppress early acoustic oscillations in primary CMB, and adds phase shift. SPT+WMAP: N=3.86 ± 0.42 € 2 Helium: Usually assume YP=0.24, predicted by BBN: YP = 0.2485+0.0016[(273.9Ωbh -6) +100 (S-1)] More helium decreases electron density, increasing damping. Yp= 0.30 ± 0.03 (SPT+WMAP). SPT, Keisler et al. 2011 Bounds on cosmic strings From shape of spectrum, cosmic strings cannot be dominant source of anisotropy. May be sub-dominant. Expected spectrum is uncertain. We take Nambu string sims as in Battye & Moss 2010. Find upper limits for ACT+WMAP: Gμ < 1.6 x 10-7 (95%) (pre-ACT was 2.6x10-7) Spectral index prefers to be less than unity (0.963±0.013), disfavoring hybrid inflation models predicting n~1 Dunkley et al. 2011 Limitations of primary CMB • CMB geometric degeneracy: distance depends on contents, and expansion rate. • Can balance distance with geometry to keep peaks in same place. • Can’t see late-time structure growth ✖ LCDM The late universe: CMB lensing Large scale structure potentials gravitationally deflect CMB photons by a lensing deflection angle d(n), typically few arcmins. Measurement of the deflection field is a measurement of matter fluctuations AND the geometry of the universe. ACT detection of the lensing power spectrum Das, Sherwin et al. 2011 • 4-sigma detection, measures amplitude of matter fluctuations at z~0.5-3 to 12%. • Direct gravitational probe of integrated dark matter to z~1100. • Tests DE and neutrinos CMB-only preference for Λ Sherwin et al 2011 LCDM model favored at 3.2 sigma over best model with no Λ Sherwin, JD et al 2011 Coming soon… Planck Planck launched May 2009. First results Jan 2011; first cosmology results due Jan 2013, first survey data already taken. • Planck is working well. Projected to measure higher acoustic peaks – to l~2000 – to better precision than ACT/ SPT, over whole sky. • Measure inflation through spectral index, and non-Gaussianity, σ(fnl)~5 • Probe unusual high energy signatures (e.g. Neff forecast to σ ~ 0.2) • Measure neutrino mass through lensing spectrum (and with ACTPol to 0.1 eV). Summary • The small-scale CMB sky has been mapped by the Atacama Cosmology Telescope, and the South Pole Telescope, over a few percent of sky. • The ΛCDM model continues to fit the data. ACT and SPT’s longer level arm better constrains inflationary parameters, and probes non-standard physics (e.g. relativistic species, primordial helium, cosmic strings). • ACT has now detected the lensing power spectrum. It allows us to see evidence for Dark Energy from the CMB alone, and promises to better measure neutrino mass. • ACT and SPT have finished taking data, and the final analyses are underway. Planck is working well and results are due early 2013. ACTPol and SPTPol then expected to start next year. .