Using the latest physical modeling and constrained by the most recent data,we develop a phenomenological parameterized model of the contributions tointensity and polarization maps at millimeter wavelengths from externalgalaxies and Sunyaev-Zeldovich effects. We find such modeling to be necessaryfor estimation of cosmological parameters from Planck data. For example,ignoring the clustering of the infrared background would result in a bias inn_s of 7 sigma. We show that the simultaneous marginalization over a fullforeground model can eliminate such biases, while increasing the statisticaluncertainty in cosmological parameters by less than 20%. The small increases inuncertainty can be significantly reduced with the inclusion ofhigher-resolution ground-based data. The multi-frequency analysis we employ involves modeling 46 total powerspectra and marginalization over 17 foreground parameters. We show that we canalso reduce the data to a best estimate of the CMB power spectra, and just twoprincipal components (with constrained amplitudes) describing residualforeground contamination.
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