## Abstract

Measurements of the post-reionization 21-cm 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 21-cm 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 21-cm bispectrum can be adequately modelled using the predictions of second-order 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 21-cm 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 non-Gaussianity using the 21-cm bispectrum.

Original language | English |
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Pages (from-to) | 2880-2889 |

Number of pages | 10 |

Journal | Monthly Notices of the Royal Astronomical Society |

Volume | 490 |

Issue number | 2 |

DOIs | |

State | Published - 1 Dec 2019 |

Externally published | Yes |

## Keywords

- Cosmology: theory
- Diffuse radiation
- Large-scale structure of Universe
- Methods: statistical

## ASJC Scopus subject areas

- Astronomy and Astrophysics
- Space and Planetary Science