CBI Temperature and Polarization Observations 2002-2005

Product Name
Band Powers


This file contains the fine-binned CBI polarization bandpowers and band-power Fisher matrix needed for doing parameter analysis with the CBI power spectrum. It is formatted for use with COSMOMC.

System requirements: There are no special system requirements - everything is saved as text files. It is formatted for use with COSMOMC, but can be easily modified by the user if other formats are required.

The spectrum is contained in CBIpol_2.0_final.newdat This data file should work as-is with current versions of COSMOMC (Lewis & Bridle, 2002)

File format:

  • first line - location of window functions (should be properly set).
  • second line - total bands in each polarization. Order is TT,EE,BB,TB,TE,EB
  • next lines (BAND_SELECTION) - select which bands are to be used in parameter fitting. As mentioned in the paper, we drop the lowest T bin (both in TT and TE).
  • next line: (1 1.00 0.026) - only number of relevance is 0.026, which is the CBI calibration uncertainty in power (1.3% in amplitude) (ignorable line) iliketype - COSMOMC/.newdat format support offset-lognormal approximation to the likelihood (Bond, Jaffe, and Knox 2000).
    iliketype=2 lets the use of the offset-lognormal approximation be specified for each band individually. We turn it on for TT, EE, and BB, and turn it off for TE.

  • Next is a block for each polarization in the file. This contains the name of the polarization, then one line containing the spectrum for each band power in the polarization. The fields are:
  • 1) Band #
    2) Power spectrum (l(l+1)C_l/2pi, in uK2)
    3) and 4) - error bars.
    5) noise spectrum, used in the offset-lognormal approximation.
    6) and 7) the lower/upper ell range contained in the band.
    8) the iliketype flag for the band. 1 means use offset-lognormal, 0 means Gaussian.

  • Then a block containing the same-band correlations between band-powers. Ones along the diagonal,
    with the off-diagonal terms the degree of correlation between bands.
  • Finally, the Fisher matrix for the entire spectrum (all polarizations). Units are in uK4.
    This full matrix is used when calculating the likelihood of a spectrum in COSMOMC.
  • There are also files that contain the band-power window functions. There is one file for each band. Columns are:

  • 1) ell
    2)-5) W_ell/ell for each polarization. Columns are normalized, so expected C_ell is sum(W_ell,PP')C_ell,PP' over ell and polarizations PP'.

The above information is taken from this CBI page, published on 2006-11-07, and from the ReadMe file in the ApJ online supplement.

Additional Details:

* Sievers et al. (2007), "Implications of the Cosmic Background Imager Polarization Data", ApJ, 660, 976. ADS

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