The effect of bandpass uncertainties on component separation

Kavli Affiliate: Sarah Church

| First 5 Authors: Sarah Church, Lloyd Knox, Martin White, ,

| Summary:

Multi-frequency measurements of the microwave sky can be decomposed into maps
of distinct physical components such as the cosmic microwave background (CMB)
and the Sunyaev-Zel’dovich (SZ) effect. Each of the multi–frequency
measurements is a convolution of the spectrum on the sky with the bandpass of
the instrument. Here we analytically calculate the contamination of the
component maps that can result from errors in our knowledge of the bandpass
shape. We find, for example, that for Planck an unknown 10% ramp across each
band results in a CMB map dT = dT_{CMB} – 4.3e-3 dT_{SZ} plus the usual
statistical noise. The variance of this contaminant is more than a factor of
100 below the noise variance at all angular scales and even further below the
CMB signal variance. This contamination might lead to an error in the velocity
of rich clusters inferred from the kinetic SZ effect, however the error is
negligible, O(50 km/s), if the bandpass is known to 10%. Bandpass errors might
be important for future missions measuring the CMB-SZ correlation.

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