Imprint of Reionization on the Cosmic Microwave Background Bispectrum
Abstract
We study contributions to the cosmic microwave background (CMB) bispectrum from nonGaussianity induced by secondary anisotropies during reionization. Largescale structure in the reionized epoch both gravitationally lenses CMB photons and produces Doppler shifts in their temperature from scattering off electrons in infall. The resulting correlation is potentially observable through the CMB bispectrum. The secondorder OstrikerVishniac effect also couples to a variety of linear secondary effects to produce a bispectrum. For the currently favored flat cosmological model with a low matter content and small optical depth in the reionized epoch τ<~0.3, however, these bispectrum contributions are well below the detection threshold of MAP and at or below that of Planck, given their cosmic and noise variance limitations. At the upper end of this range, they can serve as an extra source of noise for measurements with Planck of either primordial nongaussianity or that induced by the correlation of gravitational lensing with the integrated SachsWolfe and the thermal SunyaevZel'dovich effects. We include a discussion of the general properties of the CMB bispectrum, its configuration dependence for the various effects, and its computation in the Limber approximation and beyond.
 Publication:

The Astrophysical Journal
 Pub Date:
 May 2000
 DOI:
 10.1086/308799
 arXiv:
 arXiv:astroph/9910397
 Bibcode:
 2000ApJ...534..533C
 Keywords:

 Cosmology: Cosmic Microwave Background;
 Cosmology: Theory;
 Cosmology: LargeScale Structure of Universe;
 Cosmology: Gravitational Lensing;
 Astrophysics
 EPrint:
 17 pages, 10 figures (with emulateapj.sty)