I've now written two sequels to this paper, which containins further improvements.
The shaded regions indicate where the various foregrounds cause fluctuations exceeding those of COBE-normalized scale-invariant fluctuations, thus posing a substantial challenge to estimation of genuine CMB fluctuations. They correspond to dust (red), free-free emission (cyan), synchrotron radiation (magenta), and point sources (green). The heavy dashed line shows the frequency where the total foreground contribution to each multipole is minimal. The boxes indicate roughly the range of multipoles l and frequencies v probed by various CMB experiments.
Max Tegmark & George Efstathiou
An improved method for subtracting contaminants from Cosmic Microwave Background (CMB) sky maps is presented, and used to estimate how well future experiments will be able to recover the primordial CMB fluctuations. We find that the naive method of subtracting foregrounds (such as dust emission, synchrotron radiation, free-free-emission, unresolved point sources, etc) on a pixel by pixel basis can be improved by more than an order of magnitude by taking advantage of the correlation of the emission in neighboring pixels. The optimal multi-frequency subtraction method improves on simple pixel-by-pixel subtraction both by taking noise-levels into account, and by exploiting the fact that most contaminants have angular power spectra that differ substantially from that of the CMB. The results are natural to visualize in the two-dimensional plane with axes defined by multipole l and frequency v. We present a brief overview of the geography of this plane, showing the regions probed by various experiments and where we expect contaminants to dominate. We illustrate the method by estimating how well the proposed ESA COBRAS/SAMBA mission will be able to recover the CMB fluctuations against contaminating foregrounds.
Published in MNRAS, 281, 1297 (1996)
This site also contains the latest versions of two other papers of mine that recur in the text; Tegmark & Bunn 1995 and the window function paper Tegmark 1996 ("T96").