Observational Cosmology Lab University of Wisconsin-Madison Cosmic Microwave Background polarization observations with the POLAR and COMPASS experiments Christopher O’Dell Observational Cosmology Lab University of Wisconsin-Madison

TALK OUTLINE CMB Introduction CMB Polarization Description/Motivation POLAR: Experiment/Analysis/Results COMPASS and Future Prospects

Cosmic Microwave Background: 3 Characteristics 2. Spatial Anisotropy T = 2.726 K Tcmb = 2.7253 K +/- 0.66 mK 1. Spectrum T ~ 20 K

Cosmological Theories Anisotropy Data in 2001 Church, Jaffe, & Knox 2001 astro-ph/0111203

Cosmological Parameters in 2001

3rd CMB Characteristic: Polarization At last scattering, a quadrupole in temperature anisotropy generates a polarized CMB signal.

Rotation of Coordinates by angle a POLARIZATION MATH Stokes’ Parameters Intensity Linear Polarization Circular Polarization Rotation of Coordinates by angle a

The E-B Decomposition Gradient-Type (E) : Symmetric Under Rotation Symmetric Under Parity Curl-Type (B): Symmetric Under Rotation Anti-symmetric Under Parity Power Spectra: TT : Anisotropy EE : E-type Polarization BB : B-type Polarization TE : Temp-Epol Cross Correlation Zaldarriaga & Seljak, 1998

Hu & Dodelson (Annual Reviews 2002) The Four CMB Power Spectra TT TE Hu & Dodelson (Annual Reviews 2002)

Why Measure CMB Polarization?? Is a fundamental prediction of the standard cosmological model. Helps break degeneracies in determining fundamental cosmological parameters. Probes Reionization History of the Universe. B-modes are directly sensitive to primordial gravitational waves; the amplitude of the BB spectrum is proportional to the square root of the energy scale of inflation. They also help characterize the tensor-to-scalar ratio, r. Polarization is required to truly test adiabaticity of the primordial seeds of structure. Parameter estimation is seriously degraded when a mixture of initial fluctuation types is allowed. We often see something new and unexpected with each new window on the universe!

No Reionization. Prms ~ 0.5 K Zaldarriaga, 2001

Reionization at z ~ 30 Prms ~ 3.2 K t = 0.3 , Zre ~ 30 Zaldarriaga, 2001

1965 1979 1983 1995 Zre ~ 30 Reionization Peak Josh Gundersen, 2001

Polarization Observations of Large Angular Regions (POLAR) A. de Oliveira-Costa (UPenn) J. Gundersen (Miami) B. Keating (Caltech) S. Klawikowski (UW-Madison) C. O’Dell (UW-Madison) L. Piccirillo (Cardiff) N. Stebor (UW-Madison) D. Swetz (UW-Madison) M. Tegmark (UPenn) P. Timbie (UW-Madison)

The Spinning Correlation Polarimeter x y CMB  Ground Screens Ex Ey OMT Gx Gy 0°, 180° Phase Shifter Multiplier

POLAR Main Features Clean, simple design: no lenses or mirrors no magnetic or moving parts (excepting overall rotation) Corrugated conical feed horn achieves 7° beam with very low sidelobes. HEMT amplifiers (25 K noise temperature, NET ~ 800 K • sec-1/2) Commercial Cryocooler (no liquid cryogens). Frequency bands: 26-36 GHz, 3 sub-bands (plus basic sensitivity to Ix and Iy ).

Outer Ground Shield Clam-Shell Dome Clam-Shell Dome Inner Ground Shield 20 K Dewar

Q and U at ~ 20 pixels on the sky, on a 7° ring at declination 43° POLAR Scan Strategy Q and U at ~ 20 pixels on the sky, on a 7° ring at declination 43°

Atmospheric Emission at Sea Level H2O O2 Broad Line Emission Unpolarized in absence of external fields Possible O2 Zeeman splitting by earth’s B-field Negligible Will add to system noise, and affect required integration time.

Stability and Sensitivity

Polarized Foregrounds Power Spectra (30%) (3%) Josh Gundersen, 1999

from Pine Bluff, Wisconsin Observations and Data Selection March 1st – May 31st, 2000 from Pine Bluff, Wisconsin

Mapmaking Data Vector True Sky Map Noise Vector Pointing Matrix Problem : Re-construct the map from your data that is closest to the true, underlying map. Solution : “Minimum Variance Mapmaking” (not simply weighted averaging in the presence of 1/f noise)

Multi-Frequency Maps

Flat Band-Power Model : E, B Spectra have constant power at all scales, characterized by variances : (TE2 , TB2) Full 2D Likelihood: Prior Constraint that TB = 0

Modern Polarization Upper Limits and POLAR band-powers 0.1 105 Modern Polarization Upper Limits and POLAR band-powers 104 103 E-Mode Limits B-Mode Limits 100 PIQUE CBI ATCA 10 POLAR 1.0 0.1 10 100 1000

Onward! -> COMPASS UW-Madison UCSB Cardiff UC-Davis Caltech Rome III U-Miami

CMB Polarization: Full Speed Ahead! Experiment Date Total Sensitivity l-range DASI (HEMTs) Full Year 2001 ~ 1 uK 100-900 MAXIPOL (Spiderwebs) Mid May 2002 ~ 2 uK 400-2000 B2.002K (PSBs) December 2002 < 1 uK 100-1000 CBI (HEMTs) Full Year 2002 ~ 1 uK ? 600-1500 MAP (HEMTs) Ongoing (data ~ 1yr?) ??? 2-600 QUEST, BICEP, SPORT, ROPE, CAPMAP, etc. ??? PLANCK (HEMT/PSB) 2007? < 0.1 uK 2-3000