Reionization and CMB non-Gaussianity

Understand

We show how cross-correlating a high redshift external tracer field, such as the 21cm neutral hydrogen distribution and product maps involving Cosmic Microwave Background (CMB) temperature and polarisation fields, that probe mixed bispectrum involving these fields, can help to determine the reionization history of the Universe, beyond what can be achieved from cross-spectrum analysis.

• Taking clues from recent studies for the detection of primordial non-Gaussianity (Munshi & Heavens 2010), we develop a set of estimators that can study reionization using a power spectrum associated with the bispectrum (or skew-spectrum).
• We use the matched filtering inherent in this method to investigate different reionization histories.
• We check to what extent they can be used to rule out various models of reionization and study cross contamination from different sources such as the lensing of the CMB.