Removing point sources from cosmic microwave background maps

For high-precision cosmic microwave background (CMB) experiments, contamination from extragalactic point sources is a major concern. It is therefore useful to be able to detect and discard point-source-contaminated pixels using the map itself. We show that the sensitivity with which this can be done can often be greatly improved (by factors between 2.5 and 18 for the upcoming Planck mission) by a customized high-pass filtering that suppresses fluctuations due to the CMB and diffuse galactic foregrounds. This means that point-source contamination will not severely degrade the cleanest Planck channels unless current source count estimates are off by an order of magnitude. A catalog of around 40,000 sources at 857 GHz may be a useful by-product of Planck.