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An obvious question which remains is whether the structure in the maps
is thermal. For an interferometer, this proves nontrivial to address
in the image plane, since the uv sampling scales with frequency. A
simple division of the bandpass into halves, for instance, probes not
only different frequencies, but different angular scales as well.
In the maps in Figure 5 we attempt to minimize this complication by
imposing a uv cutoff to equalize the sampling at each frequency,
and by deconvolving the resulting sampling function from each map.
The primary beam envelope also scales with frequency, and each map has
been corrected by the appropriate taper, so that these represent our
best estimate of the actual sky structure at each frequency. A
scatter plot of the pixels in this field demonstrates that the maps
are consistent with a thermal spectrum.
Figure:
DASI image of a single
CMBR field corrected for the primary beam, imaged in two different
frequency ranges, 2631 GHz (left panel) and 3136 GHz (center
panel). The right panel shows the correlations in pixel values between
the two images. The images are consistent with one another,
indicating the imaged signal is thermal, as expected from the CMBR.

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Erik Leitch
20010416