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-α (Lyα) transmissions, built from the eBOSS Lyα 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 8σ. The observed quadrupole of the void-forest cross-correlation is described by a linear RSD model. The derived RSD parameter of the Lyα forest around voids is β=1.21±0.18. Our model accounts for the tomographic effect induced by the Lyα 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.
@article{arxiv.2203.11045,
title = {First measurement of the correlation between cosmic voids and the Lyman-$\alpha$ forest},
author = {Corentin Ravoux and Eric Armengaud and Julian Bautista and James Rich and Jean-Marc Le Goff and Nathalie Palanque-Delabrouille and Michael Walther and Christophe Yèche},
journal= {arXiv preprint arXiv:2203.11045},
year = {2026}
}