Modelling the post-reionization neutral hydrogen (H I) 21-cm bispectrum

Debanjan Sarkar, Suman Majumdar, Somnath Bharadwaj

Research output: Contribution to journalArticlepeer-review

13 Scopus citations


Measurements of the post-reionization 21-cm bispectrum BH I (k1, k2, k3) 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 b1 and b2, respectively. The b1 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 PH I (k). The b2 values fall sharply with decreasing z, becomes zero at z ∼ 3 and attains a nearly constant value b2 ≈ −0.36 at z < 2. We provide polynomial fitting formulas for b1 and b2 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 languageEnglish
Pages (from-to)2880-2889
Number of pages10
JournalMonthly Notices of the Royal Astronomical Society
Issue number2
StatePublished - 1 Dec 2019
Externally publishedYes


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

ASJC Scopus subject areas

  • Astronomy and Astrophysics
  • Space and Planetary Science


Dive into the research topics of 'Modelling the post-reionization neutral hydrogen (H I) 21-cm bispectrum'. Together they form a unique fingerprint.

Cite this