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Cosmic Microwave Background Radiation: z=1000 - z= 10

Cosmic Microwave Background Radiation: z=1000 - z= 10. David Spergel Princeton University. Standard Cosmological Model. General Relativity + Uniform Universe Big Bang Density of universe determines its fate + shape Universe is flat (total density = critical density) Atoms 4%

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Cosmic Microwave Background Radiation: z=1000 - z= 10

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  1. Cosmic Microwave Background Radiation:z=1000 - z= 10 David Spergel Princeton University

  2. Standard Cosmological Model • General Relativity + Uniform Universe Big Bang • Density of universe determines its fate + shape • Universe is flat (total density = critical density) • Atoms 4% • Dark Matter 23% • Dark Energy (cosmological constant?) 72% • Universe has tiny ripples • Adiabatic, scale invariant, Gaussian Fluctuations • Harrison-Zeldovich-Peebles • Inflationary models

  3. Quick History of the Universe • Universe starts out hot, dense and filled with radiation • As the universe expands, it cools. • During the first minutes, light elements form • After 500,000 years, atoms form • After 100,000,000 years, stars start to form • After 1 Billion years, galaxies and quasars

  4. Thermal History of Universe NEUTRAL radiation matter r IONIZED 103 104 z

  5. Growth of Fluctuations • Linear theory • Basic elements have been understood for 30 years (Peebles, Sunyaev & Zeldovich) • Numerical codes agree at better than 0.1% (Seljak et al. 2003)

  6. Temperature 85% of sky cosmic variance Best fit model 1 deg Temperature-polarization

  7. CBI Results • ACBAR, VSA also tests physics of damping tail • Important confirmation of theory • Improves parameter constraints Readhead et al. (2004) Astro-ph/0409569

  8. Structure Formation

  9. Model Predicts Universe Today SDSS Tegmark et al. Astro-ph/0310723 Verde et al. (2003)

  10. Consistent Parameters

  11. Zentner & Bullock 2003

  12. Top Hat Collapse • Focus on overdensity • Follow evolution of isolated sphere • Expansion • Turn-around • Virialization

  13. Press-Schechter Formalism • Probability of being in an overdense region • Halo Mass Function

  14. Do Stars Form in the Halos? • Can the gas cool? • Metals usually dominate the cooling --- but there are no metals • Molecular hydrogen is the only significant cooling in primordial gas • Molecular hydrogen usually forms on dust…but there is no dust • Formation through H+

  15. Numerical Simulation • CDM initial conditions • Hydrodynamics • Gas chemistry • Radiative Transfer • Simulations usually show the formation of a single massive star 100 - 1000 solar masses No fragmentation seen Abel 2003

  16. First Stars • Massive stars with no primordial metals • Very hot surface--- lots of ionizing photons • Destroys H2 -- suppresses star formation • Short-lived • Supernova explosions? • Shocks compress gas • Shocks accelerate cosmic rays-- Compton cool and produce X-rays. X-rays ionize universe and produce H2 • Gamma-ray bursts? • Enrich environment with metals

  17. Can We Observe the First Stars? • Direct detection of high z objects • Galaxies • Gamma Ray Bursts • Quasar • Remnants • Low z stars • Chemical Contamination • Reionization

  18. Effects of Reionization on CMB • Temperature Power Spectrum • Suppression of fluctuations at l > 40 • Generation of new fluctuations at l > 10 • Generation of small scale fluctuations • Polarization • Generates large scale temperature polarization correlation • Generates large scale polarization-polarization correlation

  19. Reionization andTemperature Spectrum • Suppression of small scale fluctuations • Additional fluctuations generated on large scales • Degenerate with variations in slope Suppression exp(-2t)

  20. CMB Polarization • CMB polarization can be split into two pieces: E and B • Scattering converts local temperature quadrupole into E signal • Generates TE and EE signal

  21. EE Polarization Signal • Amplitude and peak position sensitive to reionization history Holder & Hu 2003

  22. Doppler Effect Contribution • Vanishes to linear order (except at the largest scales) • Doesn’t vanish to 2nd order (Ostriker-Vishniac effect) • Inhomogeneous reionization leads to additional fluctuations

  23. Why Is Polarization Difficult to Observe? • Weak signal • signal is statistical rather than a detection in each pixel • Foregrounds • Synchrotron (dominant) • Dust • Systematic Uncertainties

  24. WMAP Results • Significant uncertainty in reionization redshift • Will improve with more data • Polarization auto-correlation • Dt/t~0.1 in 4 year data

  25. Current Estimate of Optical Depth • Significant uncertainty • Temperature data pushes fit towards low tau • Polarization data pushes fit towards high tau

  26. ACT:The Next Step • Atacama Cosmology Telescope • Funded by NSF • Will measure CMB fluctuations on small angular scales • Probe the primordial power spectrum and the growth of structure

  27. Princeton PENN CatÓlica Toronto Haverford CUNY ACT COLLABORATIONS Government Labs Museums Schools …united through research, education and public outreach.

  28. Simulations of mm-wave data. Survey area High quality area 150 GHz SZ Simulation MBAC on ACT 1.7’ beam PLANCK 2X noise MAP PLANCK

  29. Where will we be with CMB Bond et al. astro-ph/046195

  30. Cosmic Timeline for ACT Science • First galaxies • Universe is reionized • Ostriker-Vishniac/KSZ • Surveys of Sunyaev-Zel’dovich (SZ) clusters • Diffuse thermal SZ Cosmic Microwave Background • N(mass,z) – Evolution of Cosmic Structure • Lensing of the CMB • The growth of structure is sensitive to w and mn • Additional cross-checks from correlations among effects • Extraction of cosmological parameters • Initial conditions for structure formation now z = 1000 t = 4 x 104 yrs z = 7 t = 3 x 106 yrs z = 1 t = 1 x 109 yrs z = .25 t = 12 x 109 yrs Primary CMB CMB Lensing OV/KSZ Diffuse Thermal SZ Cluster Surveys

  31. Sunyaev-Zel’dovich (SZ) clusters Coma Cluster Telectron = 108 K e- e- e- e- e- e- e- Cosmic Microwave Background e- e- X-ray Flux: Mass Optical: Redshift and Mass mm-Wave: SZ – Compton Scattering

  32. SZ Signature Hot electron gas imposes a unique spectral signature 145 GHz decrement 220 GHz null 270 GHz increment NO SZ Contribution in Central Band 1.4°x 1.4°

  33. Coordinated Cluster Measurements Identify and measure >500 clusters in an unbiased survey with multi-wavelength observations Galaxy Cluster Cosmic Microwave Background HOT Electrons • Mass limits of 3 x 1014 estimated from simulations • Science derived from N(mass,z)

  34. CMB Lensing of the CMB • Lensing arises from integrated mass fluctuations along the line of sight. • The CMB acts as a fixed distance source, removing the degeneracy inherent to other lensing measurements. • Signal at l = 1000-3000 • Image distortion – only a minor effect in the power spectrum. • Must have a deep, high fidelity map to detect this effect. -1850 (K) 0 1820 1.4°x 1.4°

  35. Lensing of the CMB -34 (K) 0 34 • RMS signal well above noise floor. • Isolate from SZ and point sources spectrally. • Identify with distinctive 4-point function. Lensing Signal 2% of CMB RMS 1.4°x 1.4°

  36. Cross-Correlating Lensing and CMB • CMB provides a source plane at z = 1100 with very well determined statistical properties (but poorer statistics) • CMB + Quasar & Galaxy Counts will measure bias • CMB lensing+ Galaxy lensing cross-correlation improves parameter measurements by roughly a factor of 3 (Mustapha Ishak) CMB + SN Add Lensing CMB + Lensing X-correlate

  37. ACT \REGION: Target for future lensing surveys ACT will begin surveying in 2006 We already plan deep multi-band imaging with SALT of low extinction part of ACT strip (200 square degrees) Would be a very interesting target for a lensing survey

  38. ACT is but one of several next generation CMB experiments • APEX (Atacama Pathfinder Experiment) • UCB/MPI • 1.4mm and 2 mm obs. • SZ science • SPT (South Pole Telescope) • 8m at South Pole • Chicago group (2008) • Large area • Optimized for SZ/clusters

  39. CMB Observations are an important cosmological tool • Large angle observations have helped solidify a “standard model of cosmology” that fits a host of astronomical observations • Small angle observations use this CMB backlight to probe the emergence of structure • First stars: OV effect, polarization • Cluster properties: SZ effect • Distribution of mass: lensing

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