Cross-Bispectrum Constraints from HI Intensity Mapping and Galaxy Surveys
Abstract
Future neutral hydrogen (HI) intensity mapping (IM) and optical surveys probe large-scale structure over unprecedented volumes, offering powerful constraints on cosmological models. We study the cross-correlation between the HI IM field and the galaxy density and cosmic shear fields from optical surveys. By formulating the HI-HI-galaxy and HI-HI-shear cross-bispectra, we recover sensitivity to long-wavelength radial modes otherwise removed by foreground subtraction in HI maps, evaluating their detectability for HIRAX and Rubin-LSST. Combining the probes breaks degeneracies in redshift-dependent quantities, including the f-σ8 degeneracy. Our constraints range from 0.74% to 9.8% on f and 0.073% to 3.5% on σ8 across the six redshift bins that we consider. Our constraints on the first- and second-order HI bias parameters range from 0.42% to 5.6% on bHI(1) and from 2.0% to 29% on bHI(2), while the galaxy bias constraints range from 2.6% to 11% on bgal. The HI-HI-galaxy density cross-bispectrum measurement allows us to constrain a linear scale-dependent model for the stochastic cross-correlation coefficient between HI and stars, rHI HI δg = r0 + r1 k, with a break scale of 0.14 Mpc−1. We obtain r0 constraints that range from 3.8% to 13.5% and r1 constraints that range from 7.5% to 19.9%. For cosmology, adding cross-bispectra enhances Lambda CDM constraints, notably via the HI-HI-shear cross-bispectrum. For the w0 waCDM model, the power-spectrum-only constraints on w0 and wa, including Planck priors, improve from (σw0,σwa)=(0.036,0.15) and $(0.032,0.12)$ to (σw0,σwa)=(0.014,0.057) and $(0.015,0.059)$ when adding the HI-HI-galaxy and HI-HI-shear cross-bispectra, respectively.
Related
- Constraints on Primordial Oscillatory Features from the Power Spectrum and Bispectrum of Redshift-Space Galaxy Clustering in DESI DR1
- Cosmology with post-EoR 21 cm Intensity Mapping surveys: power spectrum measurements in the last decade
- Euclid preparation. CXV. Galaxy power spectrum and bispectrum modelling
- Detection of the Galaxy--Galaxy--Temperature Skewed Bispectrum
- Analytic bispectrum covariance for galaxy survey cosmology
BibTeX
@misc{naidoo2026crossbispectrum,
title = {{Cross-Bispectrum Constraints from HI Intensity Mapping and Galaxy Surveys}},
author = {Warren Naidoo and Moumita Aich and Kavilan Moodley},
howpublished = {arXiv},
year = {2026},
month = sep,
doi = {10.48550/arxiv.2609.25389},
eprint = {2609.25389},
archivePrefix = {arXiv},
url = {https://arxiv.org/abs/2609.25389},
note = {CC0},
}
RIS
TY - UNPB
TI - Cross-Bispectrum Constraints from HI Intensity Mapping and Galaxy Surveys
AU - Warren Naidoo
AU - Moumita Aich
AU - Kavilan Moodley
PY - 2026
DA - 2026/09/21
PB - arXiv
DO - 10.48550/arxiv.2609.25389
UR - https://arxiv.org/abs/2609.25389
AB - Future neutral hydrogen (HI) intensity mapping (IM) and optical surveys probe large-scale structure over unprecedented volumes, offering powerful constraints on cosmological models. We study the cross-correlation between the HI IM field and the galaxy density and cosmic shear fields from optical surveys. By formulating the HI-HI-galaxy and HI-HI-shear cross-bispectra, we recover sensitivity to long-wavelength radial modes otherwise removed by foreground subtraction in HI maps, evaluating their detectability for HIRAX and Rubin-LSST. Combining the probes breaks degeneracies in redshift-dependent quantities, including the f-σ_8 degeneracy. Our constraints range from 0.74% to 9.8% on f and 0.073% to 3.5% on σ_8 across the six redshift bins that we consider. Our constraints on the first- and second-order HI bias parameters range from 0.42% to 5.6% on b_HI^(1) and from 2.0% to 29% on b_HI^(2), while the galaxy bias constraints range from 2.6% to 11% on b_gal. The HI-HI-galaxy density cross-bispectrum measurement allows us to constrain a linear scale-dependent model for the stochastic cross-correlation coefficient between HI and stars, r_HI HI δ_g = r_0 + r_1 k, with a break scale of 0.14 Mpc^−1. We obtain r_0 constraints that range from 3.8% to 13.5% and r_1 constraints that range from 7.5% to 19.9%. For cosmology, adding cross-bispectra enhances Lambda CDM constraints, notably via the HI-HI-shear cross-bispectrum. For the w_0 w_aCDM model, the power-spectrum-only constraints on w_0 and w_a, including Planck priors, improve from (σ_w_0,σ_w_a)=(0.036,0.15) and $(0.032,0.12)$ to (σ_w_0,σ_w_a)=(0.014,0.057) and $(0.015,0.059)$ when adding the HI-HI-galaxy and HI-HI-shear cross-bispectra, respectively.
ER -