A Remark on the Estimation of Angular Power Spectra in the Presence of Foregrounds

Martin White

Published 1998-02-16Version 1

It is common practice to estimate the errors on the angular power spectrum which could be obtained by an experiment with a given angular resolution and noise level. Several authors have also addressed the question of foreground subtraction using multi-frequency observations. In such observations the angular resolution of the different frequency channels is rarely the same. In this report we point out how the ``effective'' beam size and noise level change with ell in this case, and give an expression for the error on the angular power spectrum as a function of ell.