First measurement of the correlation between cosmic voids and the Lyman-$\alpha$ forest

TL;DR

This paper presents the first detection of large-scale matter flows around cosmic voids at redshift 2.49 using Lyman-alpha forest data, revealing insights into cosmic structure growth at high redshift.

Contribution

It introduces a novel method to measure matter flows around cosmic voids using Lyman-alpha forest tomography at high redshift.

Findings

Detected RSD around voids with 8σ significance

Measured RSD parameter β = 1.21 ± 0.18

Demonstrated a new approach to study cosmic structure growth at high redshift

Abstract

We report the first detection at a median redshift $z = 2.49$ of large-scale matter flows around cosmic voids. Voids are identified within a tomographic map of large-scale Lyman-$\alpha$ (Ly$\alpha$) transmissions, built from the eBOSS Ly$\alpha$ forest sample in the SDSS Stripe 82 field. We measure the imprint of flows around voids, known as redshift-space distortions (RSD), with a statistical significance of $8\,\sigma$. The observed quadrupole of the void-forest cross-correlation is described by a linear RSD model. The derived RSD parameter of the Ly$\alpha$ forest around voids is $\beta = 1.21 \pm 0.18$. Our model accounts for the tomographic effect induced by the Ly$\alpha$ data being located along parallel quasar lines of sight. This work presents a novel approach to observing the growth of cosmic structures at redshifts currently inaccessible to galaxy surveys.