Scale-dependent galaxy bias, CMB lensing-galaxy cross-correlation, and neutrino masses

TL;DR

This paper introduces a new method to model scale-dependent galaxy bias using CMB lensing-galaxy cross-correlation, significantly improving neutrino mass constraints from galaxy power spectrum data.

Contribution

The paper presents a novel approach to constrain galaxy bias $b(k)$ via CMB lensing-galaxy cross-correlation, enhancing neutrino mass bounds from large-scale structure data.

Findings

Detected non-zero scale dependence of galaxy bias.

Achieved a 95% C.L. upper bound on neutrino mass of 0.19 eV.

Demonstrated improved neutrino mass constraints with the new method.

Abstract

One of the most powerful cosmological datasets when it comes to constraining neutrino masses is represented by galaxy power spectrum measurements, $P_{gg}(k)$. The constraining power of $P_{gg}(k)$ is however severely limited by uncertainties in the modeling of the scale-dependent galaxy bias $b(k)$. In this Letter we present a new method to constrain $b(k)$ by using the cross-correlation between the Cosmic Microwave Background (CMB) lensing signal and galaxy maps ($C_\ell^{\rm \kappa g}$) using a simple but theoretically well-motivated parametrization for $b(k)$. We apply the method using $C_\ell^{\rm \kappa g}$ measured by cross-correlating Planck lensing maps and the Baryon Oscillation Spectroscopic Survey (BOSS) Data Release 11 (DR11) CMASS galaxy sample, and $P_{gg}(k)$ measured from the BOSS DR12 CMASS sample. We detect a non-zero scale-dependence at moderate significance, which suggests that a proper modeling of $b(k)$ is necessary in order to reduce the impact of non-linearities and minimize the corresponding systematics. The accomplished increase in constraining power of $P_{gg}(k)$ is demonstrated by determining a 95% C.L. upper bound on the sum of the three active neutrino masses $M_{\nu}$ of $M_{\nu}<0.19\, {\rm eV}$. This limit represents a significant improvement over previous bounds with comparable datasets. Our method will prove especially powerful and important as future large-scale structure surveys will overlap more significantly with the CMB lensing kernel providing a large cross-correlation signal.