Febaruary 22, 2008Scott Dodelson1 Cosmic Microwave Background Presentation to P5

Febaruary 22, 2008Scott Dodelson2 Observations of CMB temperature anisotropies are the basis of modern cosmology

Febaruary 22, 2008Scott Dodelson3 Temperature anisotropies have secured the notion of a dark sector …

Febaruary 22, 2008Scott Dodelson4 … 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, 2008Scott Dodelson5 Evidence for Inflation CMB polarization sensitive to gravity waves produced during inflation. CMB Polarization experiments probe physics at the GUT-scale.

Febaruary 22, 2008Scott Dodelson6 Unpolarized isotropic radiation Compton scattering does not produce polarization

Febaruary 22, 2008Scott Dodelson7 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, 2008Scott Dodelson8 Current Results Samtleben, Staggs, & Winstein 2008

Febaruary 22, 2008Scott Dodelson9 Polarization field composed of E- and B- modes E B Weiss Report 2005

Febaruary 22, 2008Scott Dodelson10 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, 2008Scott Dodelson11 Amplitude of B-mode signal tied to physics of inflation Tensor/scalar ratio teaches us about the GUT scale physics driving inflation.

Febaruary 22, 2008Scott Dodelson12 Expected Signal Boyle, Steinhardt, Turok (2005) 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?

Febaruary 22, 2008Scott Dodelson13 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, 2008Scott Dodelson14 Extract gravitational potential along the line of sight Potential depends on neutrino mass. Could detect 0.05 eV signal (which must be there!) Seljak & Hirata 2003 Input potential Extracted from CMB simluation

Febaruary 22, 2008Scott Dodelson15 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 (V inf ~2 x10 16 GeV) might be best we can do Weiss Report 2005 Dashed lines estimates of residual foreground noise

Febaruary 22, 2008Scott Dodelson16 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, 2008Scott Dodelson17 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, 2008Scott Dodelson18 Funding Weiss Report 2005 Code R eliminated from NASA

Febaruary 22, 2008Scott Dodelson19 US-Funded CMB Experiments ExperimentFunding Estimate ($M/yr) Comments BICEPNSF 100,150 GHz; Observing for 2 yrs; 3 rd season upcoming; 100 detectors; will get to r=0.1. Plans for detector upgrades PolarBearNSF 90,150,200 GHz; NSF Funded for 5 yrs, to start in 2009 EBEXNASA 90,150,200 GHz; Balloon Funded by NASA; test flight this summer; science flight 2010 SPIDERNASA 90,150,220 GHz; Balloon funded by NASA; test flight 2010; science flight 2011 ACTNSF 1.5Planning upgrade to do polarization SPTNSF 3Planning upgrade to do polarization R&DNASA 4 NSF 1 Technology development, theory, data analysis QUIETNSF 44,90 GHz; NSF funded first phase + Now applying for 2 nd phase WMAPNASA 3Funding continues through at least 2010 PlanckNASA 8Launch this year OtherAll 1-2COFE, BLAST, NERSC, … Total27

Febaruary 22, 2008Scott Dodelson20 DOE Technology Backend Electronics designed at LBNL Center for Nanoscale Materials (Argonne) SiDet (FNAL) TES detectors for CDMS DOE institutions have technological resources to contribute significantly to this field CMB Data Analysis at NERSC

Febaruary 22, 2008Scott Dodelson21 The Next Next Big Thing? Redshifted 21 cm studies can produce 3D maps of neutral H

Febaruary 22, 2008Scott Dodelson22 21 cm Surveys

Febaruary 22, 2008Scott Dodelson23 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, 2008Scott Dodelson24 Foregrounds