Constraints from CMB lensing tomography with projected bispectra

TL;DR

This paper measures and analyzes the galaxy bispectrum and its cross-correlation with CMB lensing, demonstrating its utility in constraining cosmological parameters like  and m, and showing consistency with traditional methods.

Contribution

It introduces a generalized filtered-squared bispectrum approach for cross-correlations and performs the first combined cosmological analysis using projected power spectra and bispectra.

Findings

High significance detection of galaxy bispectrum and galaxy-galaxy-convergence bispectrum.

The bispectrum is well described by a tree-level model with linear galaxy bias.

Combined analysis constrains  and m parameters consistent with traditional methods.

Abstract

We measure the angular power spectrum and bispectrum of the projected overdensity of photometric DESI luminous red galaxies, and its cross-correlation with maps of the Cosmic Microwave Background lensing convergence from \planck. This analysis is enabled by the use of the ``filtered-squared bispectrum'' approach, introduced in previous work, which we generalise here to the case of cross-correlations between multiple fields. The projected galaxy bispectrum is detected at very high significance (above $30\sigma$ in all redshift bins), and the galaxy-galaxy-convergence bispectrum is detected above $5\sigma$ in the three highest-redshift bins. We find that the bispectrum is reasonably well described over a broad range of scales by a tree-level prediction using the linear galaxy bias measured from the power spectrum. We carry out the first cosmological analysis combining projected power spectra and bispectra under a relatively simple model, and show that the galaxy bispectrum can be used in combination with the power spectrum to place a constraint on the amplitude of matter fluctuations, $\sigma_8$, an on the non-relativistic matter fraction $\Omega_m$. We find that data combinations involving the galaxy bispectrum recover constraints on these parameters that are in good agreement with those found from the traditional ``2$\times$2-point'' combination of galaxy-galaxy and galaxy-convergence power spectra, across all redshift bins.