Delensing CMB polarization with external datasets

• Published in: Journal of cosmology and astroparticle physics Vol. 2012; no. 6; pp. 1 - 21
• Main Authors: Smith, Kendrick M, Hanson, Duncan, LoVerde, Marilena, Hirata, Christopher M, Zahn, Oliver
• Format: Journal Article
• Language: English
• Published: United States 01.06.2012
• Subjects: ALGORITHMS; ASTROPHYSICS; ASTROPHYSICS, COSMOLOGY AND ASTRONOMY; Constraining; COSMOLOGY; Formalism; GRAVITATIONAL LENSES; GRAVITATIONAL WAVES; Gravity waves; MONTE CARLO METHOD; Monte Carlo methods; POLARIZATION; RELICT RADIATION; RESOLUTION; SENSITIVITY; STOCHASTIC PROCESSES; UNIVERSE
• ISSN: 1475-7516; 1475-7516
• DOI: 10.1088/1475-7516/2012/06/014

One of the primary scientific targets of current and future CMB polarization experiments is the search for a stochastic background of gravity waves in the early universe. As instrumental sensitivity improves, the limiting factor will eventually be B-mode power generated by gravitational lensing, which can be removed through use of so-called "delensing" algorithms. We forecast prospects for delensing using lensing maps which are obtained externally to CMB polarization: either from large-scale structure observations, or from high-resolution maps of CMB temperature. We conclude that the forecasts in either case are not encouraging, and that significantly delensing large-scale CMB polarization requires high-resolution polarization maps with sufficient sensitivity to measure the lensing B-mode. We also present a simple formalism for including delensing in CMB forecasts which is computationally fast and agrees well with Monte Carlos.