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Published June 9, 2009 | Published
Book Section - Chapter Open

Prospects for polarized foreground removal


In this report we discuss the impact of polarized foregrounds on a future CMBPol satellite mission. We review our current knowledge of Galactic polarized emission at microwave frequencies, including synchrotron and thermal dust emission. We use existing data and our understanding of the physical behavior of the sources of foreground emission to generate sky templates, and start to assess how well primordial gravitational wave signals can be separated from foreground contaminants for a CMBPol mission. At the estimated foreground minimum of ∼100 GHz, the polarized foregrounds are expected to be lower than a primordial polarization signal with tensor‐to‐scalar ratio r = 0.01, in a small patch (∼1%) of the sky known to have low Galactic emission. Over 75% of the sky we expect the foreground amplitude to exceed the primordial signal by about a factor of eight at the foreground minimum and on scales of two degrees. Only on the largest scales does the polarized foreground amplitude exceed the primordial signal by a larger factor of about 20. The prospects for detecting an r = 0.01 signal including degree‐scale measurements appear promising, with 5σ_r∼0.003 forecast from multiple methods. A mission that observes a range of scales offers better prospects from the foregrounds perspective than one targeting only the lowest few multipoles. We begin to explore how optimizing the composition of frequency channels in the focal plane can maximize our ability to perform component separation, with a range of typically 40 ≲ ν ≲ 300 GHz preferred for ten channels. Foreground cleaning methods are already in place to tackle a CMBPol mission data set, and further investigation of the optimization and detectability of the primordial signal will be useful for mission design.

Additional Information

© 2009 American Institute of Physics. Published online 09 June 2009. This research was partly funded by NASA Mission Concept Study award NNX08AT71G S01. We thank Scott Dodelson for coordination of the CMBPol Theory and Foregrounds workshop and proceedings, and acknowledge the organizational work of the Primordial Polarization Program Definition Team. We thank David Spergel and Alex Lazarian for useful comments. JD acknowledges support from an RCUK fellowship. GR is supported by the US Planck Project, which is funded by the NASA Science Mission Directorate. We thank the WMAP team for making maps available on LAMBDA, and acknowledge the use of the Planck Sky Model, developed by the Component Separation Working Group (WG2) of the Planck Collaboration. We acknowledge use of the HEALPix, PolSpice, CAMB, and CMBFAST packages

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