Constraining Neutrino Mass with the Tomographic Weak Lensing Bispectrum

TL;DR

This study investigates how massive neutrinos affect the weak lensing shear bispectrum, demonstrating that combining bispectrum and power spectrum measurements enhances constraints on key cosmological parameters.

Contribution

It introduces the use of the tomographic weak lensing bispectrum from simulations to constrain neutrino mass and cosmological parameters, showing the added value of bispectrum measurements.

Findings

Massive neutrinos suppress bispectrum amplitude more than the power spectrum.

Bispectrum constraints are comparable to power spectrum constraints.

Combining bispectrum and power spectrum improves parameter constraints significantly.

Abstract

We explore the effect of massive neutrinos on the weak lensing shear bispectrum using the Cosmological Massive Neutrino Simulations. We find that the primary effect of massive neutrinos is to suppress the amplitude of the bispectrum with limited effect on the bispectrum shape. The suppression of the bispectrum amplitude is a factor of two greater than the suppression of the small scale power-spectrum. For an LSST-like weak lensing survey that observes half of the sky with five tomographic redshift bins, we explore the constraining power of the bispectrum on three cosmological parameters: the sum of the neutrino mass $\sum m_\nu$, the matter density $\Omega_m$ and the amplitude of primordial fluctuations $A_s$. Bispectrum measurements alone provide similar constraints to the power spectrum measurements and combining the two probes leads to significant improvements than using the latter alone. We find that the joint constraints tighten the power spectrum $95\%$ constraints by $\sim 32\%$ for $\sum m_\nu$, $13\%$ for $\Omega_m$ and $57\%$ for $A_s$ .