Modelling the postreionization neutral hydrogen (H I) 21cm bispectrum
Abstract
Measurements of the postreionization 21cm bispectrum B_{H I} }({k_1},{k_2},{k_3}) using various upcoming intensity mapping experiments hold the potential for determining the cosmological parameters at a high level of precision. In this paper, we have estimated the 21cm bispectrum in the z range 1 ≤ z ≤ 6 using seminumerical simulations of the neutral hydrogen (H I) distribution. We determine the k and z range where the 21cm bispectrum can be adequately modelled using the predictions of secondorder perturbation theory, and we use this to predict the redshift evolution of the linear and quadratic H I bias parameters b_{1} and b_{2}, respectively. The b_{1} values are found to decrease nearly linearly with decreasing z, and are in good agreement with earlier predictions obtained by modelling the 21cm power spectrum P_{H I} }(k). The b_{2} values fall sharply with decreasing z, becomes zero at z ∼ 3 and attains a nearly constant value b_{2} ≈ 0.36 at z < 2. We provide polynomial fitting formulas for b_{1} and b_{2} as functions of z. The modelling presented here is expected to be useful in future efforts to determine cosmological parameters and constrain primordial nonGaussianity using the 21cm bispectrum.
 Publication:

Monthly Notices of the Royal Astronomical Society
 Pub Date:
 December 2019
 DOI:
 10.1093/mnras/stz2799
 arXiv:
 arXiv:1907.01819
 Bibcode:
 2019MNRAS.490.2880S
 Keywords:

 methods: statistical;
 cosmology: theory;
 diffuse radiation;
 largescale structure of Universe;
 Astrophysics  Cosmology and Nongalactic Astrophysics
 EPrint:
 10 pages, 8 figures, 1 table, MNRAS, submitted