Wilkinson Microwave Anisotropy Probe DR5
Inverse Covariance Matrices
HEALPix, nested, Res 4/NSide=16
The inverse covariance (N-1) matrices supplied with the higher resolution maps do not fullly characterize the pixel-to-pixel noise in the res 4 maps. Therefore a more accurate and much larger inverse covariance matrix is supplied for each map as a separate product. These are supplied in one of two forms:
All the inverse covariance matrices have had σ02 divided out of them. These factors may be found in skymap_info.html.
The elements corresponding to the Galatic plane pixels as defined by the processing mask were set to zero. Therefore, the matrices as supplied are singular. To make them non-singular, the row and the column corresponding to each zero element of the diagonal need to be deleted.
The matrices include a contribution due to uncertainty in the loss imbalance coefficients in each differencing assembly (Jarosik et al. 2010). In previous releases, this uncertainty was fully marginalized--equivalent to assuming no information about these coefficients. In the latest release of the matrices for raw Stokes Q and U maps (those without foreground cleaning), a true 1-σ uncertainty was incorporated into this term.