Foregrounds and Forecasts for the Cosmic Microwave Background

One of the main challenges facing upcoming CMB experiments will be todistinguish the cosmological signal from foreground contamination. We present acomprehensive treatment of this problem and study how foregrounds degrade theaccuracy with which the Boomerang, MAP and Planck experiments can measurecosmological parameters. Our foreground model includes not only thenormalization, frequency dependence and scale dependence for each physicalcomponent, but also variations in frequency dependence across the sky. Whenestimating how accurately cosmological parameter can be measured, we includethe important complication that foreground model parameters (we use about 500)must be simultaneously measured from the data as well. Our results are quiteencouraging: despite all these complications, precision measurements of mostcosmological parameters are degraded by less than a factor of 2 for our mainforeground model and by less than a factor of 5 in our most pessimisticscenario. Parameters measured though large-angle polarization signals suffermore degradation: up to 5 in the main model and 25 in the pessimistic case. Theforegrounds that are potentially most damaging and therefore most in need offurther study are vibrating dust emission and point sources, especially thosein the radio frequencies. It is well-known that E and B polarization containvaluable information about reionization and gravity waves, respectively.However, the cross-correlation between polarized and unpolarized foregroundsalso deserves further study, as we find that it carries the bulk of thepolarization information about most other cosmological parameters.