Category: Entertainment

Presentation Description

No description available.


Presentation Transcript


DASI Detection of CMB Polarization


DASI PolarizationTeam U. Chicago John Kovac  Ph. D. Thesis Erik Leitch Clem Pryke John Carlstrom Mark Dragovan Winterovers: B. Reddall & E. Sandberg U.C.Berkeley N. W. Halverson W. L. Holzapfel


DASI, March 2000


DASI 1st Season Results DASI papers I, II & II (astro-ph/0104488 – 90) April 2001


from W. Hu’s web page Due to Thomson scattering – polarization must be there if theoretical framework is correct CMB Polarization

Why measure CMB Polarization?: 

Why measure CMB Polarization? Directly measures dynamics in early universe Critical test of the underlying theoretical framework  if it’s not there at the predicted level, we’re back to the drawing board. Future: Can triple the number of CMB observables  better constraints And, eventually, perhaps, measure the primordial gravity wave and directly test Inflation prediction and energy scale (this is going to be hard!)

CMB Polarization: 

CMB Polarization Simultaneous differencing of 2 polarization states using correlation receivers with HEMT amplifiers New 2002 limit POLAR: Keating et al. astro-ph/0107013; PIQUE: Hedman et al. astro-ph/0204438


Generating CMB Polarization Density mode velocities (hot to cold) hotter due to dopler shift Before decoupling:  electron ‘sees’ only a local monopole During decoupling:  mean free path increases and electron ‘sees’ quadrupole  scattered light is polarized E-mode from density modes (scalar fluctuations) has to be there! E & B-mode from gravity waves (tensor) hotter due to dopler shift

E-mode Polarization (curl free) : 

E-mode Polarization (curl free) Polarization parallel or perpendicular to wave vector Density (scalar) fluctuations generate only E-Polarization No curl component (‘Stokes’ law on close loop = 0)

B-mode Polarization (curl component) : 

B-mode Polarization (curl component) Polarization oriented at 45 degrees to wave vector Curl component (‘Stokes’ law on close loop  0)


Interferometer ‘cross’ circular polarization response


Add  Subtract Interferometer ‘cross’ circular polarization response


DASI polarization window functions for two baselines

DASI Achromatic Waveguide Polarizers: 

DASI Achromatic Waveguide Polarizers by John Kovac Axial Ratio, dB Frequency, GHZ  DASI BAND

Installing at South Pole for 2001 Season: 

Installing at South Pole for 2001 Season


MAPO January 2001 fully equipped modern lab at South Pole station Viper/ACBAR DASI w/ deployable ground shields Aug 15, 2002 DASI polarization update:  271 days of polarization data on 2 fields


Total intensity map On-axis leakage corrected Uncorrected polarization map ~1% of I On-axis & off-axis leakage corrected, < 0.15% DASI Polarimetry of Galactic Star-Formation Region NGC 6334


DASI Moon Polarization Map


 = 70 K Sum and Difference CMB Maps (also constructed and passed 300 data consistency tests)  = 2.7 uK


 = 70 K Sum and Difference CMB Maps (also constructed and passed 300 data consistency tests)  = 2.7 uK


Examples of s/n eigenmodes (expect 34 modes with average s/n > 1)


Sum and Difference DASI Eigenmode Polarization Maps (34 modes with average s/n > 1 modes)


Sum and Difference DASI Eigenmode Polarization Maps (34 modes with average s/n > 1 modes)


DASI single E parameter response function to concordance E spectrum B parameter window function of concordance E spectrum E parameter window function 200 400 600 800 1000 DASI Response to Scalar E-mode Polarization


DASI Constraint on Scalar E-mode Polarization Concordance expectation B E E B


Constraints on T, E, & TE E TE TE T E


T, E, B, TE Bandpowers

Goodness of Fit Tests: 

Goodness of Fit Tests Consistency with concordance model: excellent Consistency with null hypothesis: T=0: < 10-16 from Chi-square E=0: < 10-6 from Chi-square, Likelihood ratio, (Monte Carlo << 10-3) TE=0: < 0.05 from Likelihood analyses and Monte Carlo)


Foregrounds? Regions picked for exceptionally low Galactic foregrounds Thermal spectral index found Points source contamination extensively simulated (mean shift in E: 3%, rms 4%) Foregrounds should produce E and B


Summary DASI has detected E-mode CMB polarization with high confidence (~5) and at a level consistent with the theoretical prediction. TE detected at 95% C.L. and consistent with theoretical prediction. Papers will be posted at and astro-ph by end of the weekend.

Thanks to:: 

Thanks to: National Science Foundation and Raytheon Polar Services CARA The Caltech Cosmic Background Imager (CBI) team Center for Cosmological Physics

authorStream Live Help