South Pole Telescope
Filter Transfer Functions for the 2008 Season
These files contain estimated Fourier-domain filter transfer functions (TFs) for South Pole Telescope (SPT) maps of the ra5h30dec-55 field observed during the 2008 season in the 150 GHz and 220 GHz bands, produced for the first SPT data release in December 2011. They are to be used with the associated map files, which use the Sanson-Flamsteed projection or the oblique Lambert equal-area azimuthal projection.
The transfer functions are constructed by simulating observations of a map with a single Gaussian source with a FWHM of 0.75 arcminutes centered at a given pixel (pixel [1559,1559] for the Sanson-Flamsteed maps, one of nine possible pixel locations for the Lambert equal-area azimuthal maps), and subjecting those simulated observations to the data processing and filtering used for real SPT data. The input signal is then divided out from the Fourier-domain representation of the resulting maps. Regions of the Fourier plane for which the Gaussian kernel amplitude was less than 1% were set to zero to avoid numerical artifacts. The transfer functions are stored in the primary image arrays of FITS files as 3120-pixel by 3120-pixel grids, where the grid in each dimension corresponds to 0, 2π/(NT), 2*2π/(NT), ... (N/2-1)*2π/(NT), 2π/(2T), -(N/2-1)*2π/(NT), ..., -2π/(NT) where N is the number of elements (3120) and T is the sampling interval in each dimension of the map (0.25 arcminutes).
The Sanson-Flamsteed projection file for each band contains the transfer function valid for the full map. Each oblique Lambert equal-area azimuthal projection file contains the transfer function estimated for a subregion of the map covering approximately one-ninth of the map area. The two numerical tags in the file names (as well as the X_CEN/Y_CEN and RA_CEN/DEC_CEN keywords in the files) refer to the pixel locations in x and y at the location of the Gaussian kernel and the center of the mask used to define the subregion.
A complete description of the observations, data processing, calibration, instrument response, and mapmaking process for this data release is in Schaffer et al. 2011, ApJ, 743, 90.