The Cosmic Background Imager – AAS Denver, June Latest Results from the Cosmic Background Imager Steven T. Myers National Radio Astronomy Observatory Socorro, NM

The Cosmic Background Imager – AAS Denver, June A Theoretical Digression

The Cosmic Background Imager – AAS Denver, June The Cosmic Microwave Background Discovered 1965 ( Penzias & Wilson ) –2.7 K blackbody –Isotropic –Relic of hot “big bang” –Last scattering “surface” z ~ 1000 COBE 1992 –Blackbody K –3 mK dipole (Doppler) –Anisotropies 10 -5

The Cosmic Background Imager – AAS Denver, June Primary Anisotropies Courtesy Wayne Hu –

The Cosmic Background Imager – AAS Denver, June Secondary Anisotropies Courtesy Wayne Hu –

The Cosmic Background Imager – AAS Denver, June CMB Polarization Due to quadrupolar intensity field at scattering Courtesy Hu & White–

The Cosmic Background Imager – AAS Denver, June Polarization Power Spectra Hu & Dodelson ARAA 2002

The Cosmic Background Imager – AAS Denver, June CMB State of the Art: WMAP + “ext” WMAP Satellite

The Cosmic Background Imager – AAS Denver, June The Cosmic Background Imager

The Cosmic Background Imager – AAS Denver, June The Cosmic Background Imager A collaboration between –Caltech (A.C.S. Readhead PI) –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

The Cosmic Background Imager – AAS Denver, June The Instrument cm Cassegrain antennas –78 baselines 6-meter platform –Baselines 1m – 5.51m 10 1 GHz channels 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

The Cosmic Background Imager – AAS Denver, June Site – Northern Chilean Andes

The Cosmic Background Imager – AAS Denver, June The CMB and Interferometry The sky can be uniquely described by spherical harmonics –CMB power spectra are described by multipole l ( the angular scale in the spherical harmonic transform) For small (sub-radian) scales the spherical harmonics can be approximated by Fourier modes –The conjugate variables are (u,v) as in radio interferometry –The uv radius is given by l / 2  The projected length of the interferometer baseline gives the angular scale –Multipole l = 2  B / An interferometer naturally measures the transform of the sky intensity in l space convolved with aperture

The Cosmic Background Imager – AAS Denver, June Axis mount : rotatable platform

The Cosmic Background Imager – AAS Denver, June CBI Beam and uv coverage Over-sampled uv-plane –excellent PSF –allows fast gridded method (Myers et al. 2000)

The Cosmic Background Imager – AAS Denver, June New: Extended Mosaics CBI field-of-view 45’ →  l ~180 –narrow CMB peaks, mosaicing required!

The Cosmic Background Imager – AAS Denver, June New: CBI Results Noise Power Resid. Sources

The Cosmic Background Imager – AAS Denver, June CBI , WMAP, ACBAR

The Cosmic Background Imager – AAS Denver, June New: Cosmological Parameters Data: –WMAP –CBI + WMAP –CBI + ALL Priors: –flat  tot =1 –45 < H 0 < 90 –t 0 > 10 Gyr Reference: –Readhead et al. ApJ in press (2004) astro-ph/

The Cosmic Background Imager – AAS Denver, June New: Running Spectral Index? Data: –WMAP –CBI + WMAP –CBI + ALL + LSS prior Weak Priors: –flat  tot =1 –45 < H 0 < 90 –t 0 > 10 Gyr Combination: –  8 vs.  s

The Cosmic Background Imager – AAS Denver, June Dawson et al SZE Angular Power Spectrum Smooth Particle Hydrodynamics (512 3 ) [Wadsley et al. 2002] Moving Mesh Hydrodynamics (512 3 ) [Pen 1998] 143 Mpc  8 = Mpc  8 = Mpc  8 = Mpc  8 =0.9 [Bond et al. 2002]

The Cosmic Background Imager – AAS Denver, June New: High l excess & ambient SZ? Data: –CBI + BIMA –CBI + BIMA + ACBAR Details: –non-Gaussian correction (F=3) References: –BIMA 30GHz Dawson et al –ACBAR Goldstein et al Kuo et al. 2004

The Cosmic Background Imager – AAS Denver, June SZE with CBI: z < 0.1 clusters Udomprasert 2003, PhD thesis, Caltech

The Cosmic Background Imager – AAS Denver, June CBI Polarization

The Cosmic Background Imager – AAS Denver, June Polarization Interferometry CBI receivers can observe either R or L circular pol –RR and LL measure CMB intensity (temperature) I –RL and LR measure CMB polarization Q,U

The Cosmic Background Imager – AAS Denver, June Polarization E and B modes A useful decomposition of the polarization signal is into gradient and curl modes – E and B: The CBI measures E & B “directly” !

The Cosmic Background Imager – AAS Denver, June Polarization Issues Low signal levels –High sensitivity and long integrations needed –Prone to systematics and foreground contamination Instrumental polarization –Well-calibrated system necessary –Straightforward for interferometry (leakage R↔L) Stray radiation –Sky (atmosphere) ~unpolarized (good!) –Ground highly polarized (bad!) –Scan differencing or projection necessary Computationally intensive! –covariances TT, EE, BB, TE, EB, TB plus N and C srcs –6 x 6 mosaics with scan projection C scan

The Cosmic Background Imager – AAS Denver, June DASI & WMAP Polarization Courtesy Wayne Hu –

The Cosmic Background Imager – AAS Denver, June CBI Current Polarization Data Observing since Sep 2002 in compact configuration –Data processed through May 2004 Four mosaics 02 h, 08 h, 14 h, 20 h –02h, 08h, 14h 6 x 6 fields, 45’ centers –20h deep strip 6 fields Scan subtraction/projection –observe scan of 6 fields, 3m apart = 45’ –lose on 1/6 data to differencing (cf. ½ previously) Point source projection –list of NVSS sources (extrapolation to 30 GHz unknown) –need 30 GHz GBT measurements to identify brightest srcs

The Cosmic Background Imager – AAS Denver, June CBI Polarization Projections

The Cosmic Background Imager – AAS Denver, June CBI Polarization Data Processing Massive data processing exercise –4 mosaics, 300 nights observing –more than 10 6 visibilities total! –scan projection over 3.5° requires fine gridding more than 10 4 gridded estimators Parallel computing critical –both gridding and likelihood now parallelized using MPI using 256 node/ 512 proc McKenzie cluster at CITA 2.4 GHz Intel Xeons, gigabit ethernet, 1.2 Tflops! current limitation 1 GB memory per node –code development ongoing currently 1 day per full run needed

The Cosmic Background Imager – AAS Denver, June CBI Current Polarization Data Currently data to May 2004 processed –Preliminary data analysis (still more tests pending) if you sign the non-disclosure agreement…

The Cosmic Background Imager – AAS Denver, June Conclusions CMB interferometry competitive –straightforward analysis {RR,RL} → {TT,EE,BB,TE} –polarization systematics minimized –currently only measurements of EE (WMAP pending) –but, hard to scale up due to correlator complexity CMB results –large l TT excess still significant next gen small-scale experiments (SZA) will nail this! –possible running index n s ( l ) marginal significance (probably overstated) –polarization observations successful results very preliminary! still more tests…

The Cosmic Background Imager – AAS Denver, June The CMB From NRAO HEMTs OVRO/BIMA

The Cosmic Background Imager – AAS Denver, June The CBI Collaboration Caltech Team: Tony Readhead (Principal Investigator), John Cartwright, 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.