First Detection of Cosmic Microwave Background Lensing and Lyman-{\alpha} Forest Bispectrum

TL;DR

This paper reports the first detection of a correlation between the Lyman-alpha forest and CMB lensing, providing new insights into the large-scale structure and the relation between intergalactic gas and dark matter.

Contribution

It introduces a novel measurement of the Lyman-alpha forest bispectrum via correlation with CMB lensing, testing cosmological models and the gas-dark matter relationship.

Findings

Detection at 5 sigma significance

Consistent with ΛCDM predictions

Measured Lyman-alpha forest bias

Abstract

We present the first detection of a correlation between the Lyman-$\alpha$ forest and cosmic microwave background (CMB) lensing. For each Lyman-$\alpha$ forest in SDSS-III/BOSS DR12, we correlate the one-dimensional power spectrum with the CMB lensing convergence on the same line of sight from Planck. This measurement constitutes a position-dependent power spectrum, or a squeezed bispectrum, and quantifies the non-linear response of the Lyman-$\alpha$ forest power spectrum to a large-scale overdensity. The signal is measured at 5~$\sigma$ and is consistent with the $\Lambda$CDM expectation. We measure the linear bias of the Lyman-$\alpha$ forest with respect to the dark matter distribution, and constrain a combination of non-linear terms including the non-linear bias. This new observable provides a consistency check for the Lyman-$\alpha$ forest as a large-scale structure probe and tests our understanding of the relation between intergalactic gas and dark matter. In the future, it could be used to test hydrodynamical simulations and calibrate the relation between the Lyman-$\alpha$ forest and dark matter.