Cosmic Microwave Background Presentation to P5 Febaruary 22, 2008 Scott Dodelson

Observations of CMB temperature anisotropies are the basis of modern cosmology Febaruary 22, 2008 Scott Dodelson

Temperature anisotropies have secured the notion of a dark sector … Febaruary 22, 2008 Scott Dodelson

… and pointed to inflation as the generator of perturbations Position of first peak Temporal phases set early on as evidenced by peak structure Shape of primordial spectrum close to scale-invariant Can we obtain more direct evidence for inflation? Febaruary 22, 2008 Scott Dodelson

Evidence for Inflation CMB polarization sensitive to gravity waves produced during inflation. CMB Polarization experiments probe physics at the GUT-scale. Febaruary 22, 2008 Scott Dodelson

Unpolarized isotropic radiation Compton scattering does not produce polarization Febaruary 22, 2008 Scott Dodelson

Unpolarized anisotropic radiation Compton scattering does produce polarization Require Quadrupole (small before recombination) Require Compton scattering (rare after recombination) Signals factor of 10 smaller than temperature anisotropies Generated during 2 epochs: pre-recombination (z~1000) and after reionization (z~10) Febaruary 22, 2008 Scott Dodelson

Current Results Samtleben, Staggs, & Winstein 2008 Febaruary 22, 2008 Scott Dodelson

Polarization field composed of E- and B- modes Weiss Report 2005 B Febaruary 22, 2008 Scott Dodelson

Quantum mechanical fluctuations during inflation are stretched to astronomical scales Inflation produces perturbations to scalar potential Φ and these grow to be majestic structure we see today… but also tensor perturbations Scalar perturbations source (T,E) but not B. Tensor perturbations source (T,E,B), so B-mode detection would be clear signal of inflation-produced gravity waves. Febaruary 22, 2008 Scott Dodelson

Amplitude of B-mode signal tied to physics of inflation Tensor/scalar ratio teaches us about the GUT scale physics driving inflation. Febaruary 22, 2008 Scott Dodelson

Expected Signal Models with single scalar field with polynomial potential predict: Small deviation from scale invariance r > 0.1 Confirmed by WMAP! Attempts to make more generic predictions point to r>0.01… … but this is the science risk. Will Andrei Linde abandon inflation if experiments show that r<0.01? Boyle, Steinhardt, Turok (2005) Febaruary 22, 2008 Scott Dodelson

Other Science: Lensing of Last Scattering Map Photons traveling from last scattering surface are deflected by fluctuating potential along the line of sight. Leaves a distinctive signature in observed temperature/polarization maps. Use this signature to extract gravitational potential maps and spectrum. Hu 2001 Febaruary 22, 2008 Scott Dodelson

Extract gravitational potential along the line of sight Input potential Extracted from CMB simluation Seljak & Hirata 2003 Potential depends on neutrino mass. Could detect 0.05 eV signal (which must be there!) Febaruary 22, 2008 Scott Dodelson

Challenges B signal is unknown but < 0.1 microK Characteristic double peaked (l=6 and l=100) signature E- converted to B- via lensing; lensing signal dominates on small scales Foregrounds need to be studied; if cleaned by a factor of 10, will have residual ~30nK amplitude r=0.01 (Vinf~2 x1016 GeV) might be best we can do Weiss Report 2005 Dashed lines estimates of residual foreground noise Febaruary 22, 2008 Scott Dodelson

Need Increase in Sensitivity Reaching fundamental limits on noise/detector. Need to multiplex many detectors to reach 30nK noise level. Weiss Report 2005 Febaruary 22, 2008 Scott Dodelson

Experts say … Connecting Quarks with the Cosmos (2003): “Measure the polarization of the cosmic microwave background with the goal of detecting the signature of inflation” Physics of the Universe (2004): “The three agencies will work together to develop by 2005 a roadmap for decisive measurements of both types of CMB polarization.” Task Force on Cosmic Microwave Background Research (2005): “Detector development is a particularly appropriate area for increased involvement by DOE in CMB research.” Beyond Einstein Program Assessment Committee (2007): “The Beyond Einstein scientific issues are so compelling that research in this area will be pursued for many years to come. All five mission areas in NASA’s Beyond Einstein plan address key questions that take physics and astronomy beyond where the century of Einstein left them.” Primordial Polarization Program Definition Team (PPPDT): chartered by the Astrophysics Research Program. The PPPDT reports to the Astrophysics Research Program Manager at NASA Headquarters. CMBPol Mission Concept Study (2008): Recently funded by NASA; hosting 3 workshops this summer (one at FNAL); will produce documents in preparation for the Decadel Survey Febaruary 22, 2008 Scott Dodelson

Funding Weiss Report 2005 Febaruary 22, 2008 Scott Dodelson Code R eliminated from NASA Febaruary 22, 2008 Scott Dodelson

US-Funded CMB Experiments Funding Estimate ($M/yr) Comments BICEP NSF 0.5 40’ @ 100,150 GHz; Observing for 2 yrs; 3rd season upcoming; 100 detectors; will get to r=0.1. Plans for detector upgrades PolarBear NSF 1.5 4’ @ 90,150,200 GHz; NSF Funded for 5 yrs, to start in 2009 EBEX NASA 1 8’ @ 90,150,200 GHz; Balloon Funded by NASA; test flight this summer; science flight 2010 SPIDER 20-70’ @ 90,150,220 GHz; Balloon funded by NASA; test flight 2010; science flight 2011 ACT Planning upgrade to do polarization SPT NSF 3 R&D NASA 4 NSF 1 Technology development, theory, data analysis QUIET 12’ @ 44,90 GHz; NSF funded first phase + Now applying for 2nd phase WMAP NASA 3 Funding continues through at least 2010 Planck NASA 8 Launch this year Other All 1-2 COFE, BLAST, NERSC, … Total 27 Febaruary 22, 2008 Scott Dodelson

DOE Technology SiDet (FNAL) Backend Electronics designed at LBNL TES detectors for CDMS DOE institutions have technological resources to contribute significantly to this field CMB Data Analysis at NERSC Center for Nanoscale Materials (Argonne) Febaruary 22, 2008 Scott Dodelson

The Next Next Big Thing? Redshifted 21 cm studies can produce 3D maps of neutral H Febaruary 22, 2008 Scott Dodelson

21 cm Surveys Febaruary 22, 2008 Scott Dodelson

Conclusions CMB is the cornerstone of modern cosmology CMB polarization studies may provide evidence for inflation, non-zero neutrino mass, and the end of the Dark Ages. DOE could play a significant role, leveraging existing facilities/talents. The future is promising: many upcoming polarization projects; plans for satellite mission; 21 cm surveys may point to new directions Febaruary 22, 2008 Scott Dodelson

Foregrounds Febaruary 22, 2008 Scott Dodelson