Modeling Extragalactic Foregrounds and Secondaries for Unbiased Estimation of Cosmological Parameters From Primary CMB Anisotropy

TL;DR

This paper develops a comprehensive phenomenological model for extragalactic foregrounds and secondary effects in millimeter-wave observations, crucial for unbiased cosmological parameter estimation from CMB data.

Contribution

It introduces a detailed parameterized model of extragalactic foregrounds and demonstrates how simultaneous marginalization can eliminate biases in cosmological parameters.

Findings

Ignoring infrared background clustering biases n_s by 7 sigma

Marginalizing over foregrounds increases uncertainties by less than 20%

Including higher-resolution data reduces uncertainties further

Abstract

Using the latest physical modeling and constrained by the most recent data, we develop a phenomenological parameterized model of the contributions to intensity and polarization maps at millimeter wavelengths from external galaxies and Sunyaev-Zeldovich effects. We find such modeling to be necessary for estimation of cosmological parameters from Planck data. For example, ignoring the clustering of the infrared background would result in a bias in n_s of 7 sigma. We show that the simultaneous marginalization over a full foreground model can eliminate such biases, while increasing the statistical uncertainty in cosmological parameters by less than 20%. The small increases in uncertainty can be significantly reduced with the inclusion of higher-resolution ground-based data. The multi-frequency analysis we employ involves modeling 46 total power spectra and marginalization over 17 foreground parameters. We show that we can also reduce the data to a best estimate of the CMB power spectra, and just two principal components (with constrained amplitudes) describing residual foreground contamination.