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

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

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

4. … 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

5. 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

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

7. 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

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

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

10. 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

11. 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

12. 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

13. 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

14. 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

15. 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

16. 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

17. 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

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

19. US-Funded CMB Experiments
Funding
Estimate ($M/yr)
Comments
BICEP
NSF 0.5
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
90,150,200 GHz; NSF Funded for 5 yrs, to start in 2009
EBEX
NASA 1
90,150,200 GHz; Balloon Funded by NASA; test flight this summer; science flight 2010
SPIDER
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
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

20. 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

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

22. 21 cm Surveys
Febaruary 22, 2008
Scott Dodelson

23. 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

24. Foregrounds
Febaruary 22, 2008
Scott Dodelson