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CMB Polarization Results from the Cosmic Background Imager

CMB Polarization Results from the Cosmic Background Imager. Steven T. Myers. National Radio Astronomy Observatory Socorro, NM. The Cosmic Background Imager. A collaboration between Caltech (A.C.S. Readhead PI, S. Padin PS.) NRAO CITA Universidad de Chile University of Chicago

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CMB Polarization Results from the Cosmic Background Imager

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  1. CMB Polarization Results from the Cosmic Background Imager Steven T. Myers National Radio Astronomy Observatory Socorro, NM

  2. The Cosmic Background Imager • A collaboration between • Caltech (A.C.S. Readhead PI, S. Padin PS.) • NRAO • CITA • Universidad de Chile • University of Chicago • With participants also from • U.C. Berkeley, U. Alberta, ESO, IAP-Paris, NASA-MSFC, Universidad de Concepción • Funded by • National Science Foundation, the California Institute of Technology, Maxine and Ronald Linde, Cecil and Sally Drinkward, Barbara and Stanley Rawn Jr., the Kavli Institute, and the Canadian Institute for Advanced Research

  3. The Instrument • 13 90-cm Cassegrain antennas • 78 baselines • 6-meter platform • Baselines 1m – 5.51m • 10 1 GHz channels 26-36 GHz • HEMT amplifiers (NRAO) • Cryogenic 6K, Tsys 20 K • Single polarization (R or L) • Polarizers from U. Chicago • Analog correlators • 780 complex correlators • Field-of-view 44 arcmin • Image noise 4 mJy/bm 900s • Resolution 4.5 – 10 arcmin

  4. Other CMB Interferometers: DASI, VSA • DASI @ South Pole • VSA @ Tenerife

  5. CBI Site – Northern Chilean Andes • Elevation 16500 ft.!

  6. CBI 2000+2001, WMAP, ACBAR, BIMA • Readhead et al. ApJ, 609, 498 (2004) • astro-ph/0402359 SZE Secondary CMB Primary

  7. CBI Polarization New Results! • Brought to you by: • Readhead, T. Pearson, C. Dickinson (Caltech) • S. Myers, B. Mason (NRAO), • J. Sievers, C. Contaldi, J.R. Bond (CITA) • P. Altamirano, R. Bustos, C. Achermann (Chile) • & the CBI team! • plus guest appearance by DASI !

  8. Polarization Interferometry • CBI receivers can observe either RCP or LCP • cross-correlate RR, RL, LR, or LL from antenna pair • Correlations to Stokes parameters (I,Q,U,V) : • RR = I + V LL = I – V RL = [Q + i U] e-i2q LR = [Q – i U] ei2q • rotates with parallactic angle of detector q on sky • CMB not circularly polarized, ignore V (RR = LL = I) • Stokes to E and B • Q + i U = [E + i B] ei2Y RL = [E + i B] ei2(Y-q) • counter*-rotates with wave vector angle Y = ½ tan-1 (v/u) • circularly polarized interferometer “directly” measures E and B! • <RR RR*> = TT <RR RL*> = TE <RL RL*> = EE + BB • Interferometry works in Fourier domain • multipole l = 2p B / l for baseline B

  9. Carlstrom et al. 2003 astro-ph/0308478 2002 DASI & 2003 WMAP Polarization Courtesy Wayne Hu – http://background.uchicago.edu

  10. New: DASI 3-year polarization results! • Leitch et al. 2004 (astro-ph/0409357) 16Sep04! • EE 6.3 σ • TE 2.9 σ • consistent w/ WMAP+ext model • BB consistent with zero • no foregrounds (yet)

  11. New: DASI 3-year polarization results! • Leitch et al. 2004 (astro-ph/0409357) 16Sep04! • CMB thermal spectrum nbb=0 : found b=0.11±0.13 • vs. synchrotron b = -2.0 to -3.0 • no point sources seen in images (>15 mJy) • test against synchrotron (diffuse and point) foregrounds • relative to 8.5 mK2 at l = 300 • NO POLARIZED FOREGROUNDS DETECTED !

  12. CBI & DASI Fields galactic projection – image WMAP “synchrotron” (Bennett et al. 2003)

  13. CBI Current Polarization Data • Observing since Sep 2002 • compact configuration, maximum sensitivity, new NRAO HEMTs • Four mosaics a = 02h, 08h, 14h, 20h at d = 0° • 02h, 08h, 14h 6 x 6 fields, 20h deep strip 6 fields , 45’ centers • Scan subtraction/projection • observe scan of 6 fields, 3m apart = 45’, remove mean • lose only 1/6 data to differencing (cf. ½ previously) • Point source projection (important for TT) • list of NVSS sources (extrapolation to 30 GHz unknown) • need 30 GHz GBT measurements to know brightest • Massive computations  parallel codes • grid visibilities and max. likelihood (Myers et al. 2003) • using 256 node/ 512 proc McKenzie cluster at CITA

  14. CBI Polarization Projections

  15. New: CBI Polarization Power Spectra • 7-band fits (Dl = 150 for 600<l<1200) • bin positions well-matched to peaks & valleys • offset bins run also • narrower bins (Dl = 75) for parameters & phase fits • bin resolution limited by signal-to-noise

  16. New: Shaped Cl fits • Use WMAP’03 best-fit Cl in signal covariance matrix • bandpower is then relative to fiducial power spectrum • compute for single band encompassing all ls • Results for CBI data (sources projected from TT only) • EE likelihood vs. zero : equivalent significance 8.9 σ

  17. 25°±33° rel. phase (Dc2=1) Dc2(0°)=0.56 New: CBI EE Polarization Phase • Peaks in EE should be offset one-half cycle vs. TT • functional fit to envelope of EE plus sinusoidal modulation:

  18. New: CBI, DASI, Capmap

  19. For more details… • See talk by Jon Sievers this afternoon in the “Precison Cosmology I” session, including discussion of: • interferometry • data processing • data quality tests • cosmological parameter constraints • more plots and pictures! • Also, stay tuned for: • press release & short paper (next week) • And then… • a set of more detailed papers (including new data)

  20. Conclusions & Future • CMB polarization interferometry (CBI,DASI) • straightforward analysis {RR,RL} → {TT,EE,BB,TE} • polarization systematics minimized • CMB polarization results • EE power spectrum measured • consistent with Standard Cosmological Model™ • EE acoustic spectrum • peaks phase one-half cycle offset from TT • BB null, no polarized foregrounds detected • TE washed out in wide bandpower bins • more data (run to end of 2005) • Beyond CBI  QUIET • large format (1000 els.) coherent (MMIC) detector array

  21. The CBI Collaboration Caltech Team: Tony Readhead (Principal Investigator), John Cartwright, Clive Dickinson, Alison Farmer, Russ Keeney, Brian Mason, Steve Miller, Steve Padin (Project Scientist), Tim Pearson, Walter Schaal, Martin Shepherd, Jonathan Sievers, Pat Udomprasert, John Yamasaki. Operations in Chile: Pablo Altamirano, Ricardo Bustos, Cristobal Achermann, Tomislav Vucina, Juan Pablo Jacob, José Cortes, Wilson Araya. Collaborators: Dick Bond (CITA), Leonardo Bronfman (University of Chile), John Carlstrom (University of Chicago), Simon Casassus (University of Chile), Carlo Contaldi (CITA), Nils Halverson (University of California, Berkeley), Bill Holzapfel (University of California, Berkeley), Marshall Joy (NASA's Marshall Space Flight Center), John Kovac (University of Chicago), Erik Leitch (University of Chicago), Jorge May (University of Chile), Steven Myers (National Radio Astronomy Observatory), Angel Otarola (European Southern Observatory), Ue-Li Pen (CITA), Dmitry Pogosyan (University of Alberta), Simon Prunet (Institut d'Astrophysique de Paris), Clem Pryke (University of Chicago). The CBI Project is a collaboration between the California Institute of Technology, the Canadian Institute for Theoretical Astrophysics, the National Radio Astronomy Observatory, the University of Chicago, and the Universidad de Chile. The project has been supported by funds from the National Science Foundation, the California Institute of Technology, Maxine and Ronald Linde, Cecil and Sally Drinkward, Barbara and Stanley Rawn Jr., the Kavli Institute,and the Canadian Institute for Advanced Research.

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