The scaledependent signature of primordial nonGaussianity in the largescale structure of cosmic reionization
Abstract
The rise of largescale structure in the universe depends upon the statistical distribution of initial density fluctuations generated by inflation. While the simplest models of inflation predict an almost perfectly Gaussian distribution, moregeneral models predict primordial deviations from Gaussianity that observations might yet be sensitive enough to detect. Recent measurements of the cosmic microwave background (CMB) temperature anisotropy bispectrum by the Planck collaboration have significantly tightened observational limits on the level of primordial nonGaussianity (PNG) in the Universe, but they are still far from the level predicted by the simplest models of inflation. Probing levels of PNG below CMB sensitivities will require other methods, such as searching for the statistical imprint of PNG on the clustering of galactic haloes. During the cosmic epoch of reionization (EoR), the first stars and galaxies released radiation into the intergalactic medium (IGM) that created ionized patches whose largescale geometry and evolution reflected the underlying abundance and largescale clustering of the starforming galaxies. This statistical connection between ionized patches in the IGM and galactic haloes suggests that observations of reionization may provide another means of constraining PNG. We employ the linear perturbation theory of reionization and semianalytic models based on the excursionset formalism to model the effects of PNG on the EoR. We quantify the effects of PNG on the largescale structure of reionization by deriving the ionized density bias, i.e. the ratio of the ionized atomic to total matter overdensities in Fourier space, at small wavenumber. Just as previous studies found that PNG creates a scaledependent signature in the halo bias, so, too, we find a scaledependent signature in the ionized density bias. Our results, which differ significantly from previous attempts in the literature to characterize this PNG signature, will be applied elsewhere to predict its observable consequences, e.g. in the cosmic 21 cm background.
 Publication:

Monthly Notices of the Royal Astronomical Society
 Pub Date:
 August 2013
 DOI:
 10.1093/mnras/stt926
 arXiv:
 arXiv:1304.6411
 Bibcode:
 2013MNRAS.433.2900D
 Keywords:

 galaxies: statistics;
 cosmology: theory;
 dark ages;
 reionization;
 first stars;
 inflation;
 largescale structure of the Universe;
 Astrophysics  Cosmology and Nongalactic Astrophysics
 EPrint:
 Accepted by MNRAS with minor changes. Minor typos corrected and references added