QMASK Data Products

The five columns in the file qmask_cmbmap.dat give x, y, z, T, and sigma. The triple (x,y,z) is a pixel unit vector in equatorial coordinates, T is the measured temperature fluctuation and sigma is the rms noise, in units of uK. The noise in this map is correlated from pixel to pixel by the deconvolution technique described in Xu, et al. (2001). The full noise covariance matrix is provided in a separate file, while this file gives the square root of the diagonal elements.

The file index.dat gives information that is useful for plotting a projection of the sky map data. It provides a mapping of sky map pixel number to an (x,y) image plane in look-up table form. The first column gives the raster number in a 256 x 256 grid, the second column gives the pixel number (the 1-based row number in the data file) of the sky map data that maps to that image pixel. This column is 0 if the corresponding pixel was not observed.

The following IDL code fragment will display an image of the sky map:

READCOL, 'index.dat', P, Format='X,L'

READCOL, 'qmask_cmbmap.dat', T, Format='X,X,X,F,X'

Image = REFORM(T(P-1 > 0), 256, 256)

Image(WHERE(P-1 LT 0)) = 0

TV, BYTSCL(Image, Min=-1000, Max=1000)

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