Large-scale Lyman-alpha Emission as a Probe of the Cosmic Web

Abstract

Deep integral-field spectroscopy with KCWI, MUSE, and VIRUS is revealing faint, extended Lyman-alpha (Lyα) emission from the circumgalactic medium and, increasingly, from diffuse gas in cosmic filaments at Cosmic Noon. But this emission is a reprocessed, biased tracer of the web. Using cosmological simulations with Monte Carlo Lyα radiative transfer, I show that observable filaments are illuminated by photons escaping galaxies and their halos, coupling gas and galaxy physics across the interstellar, circumgalactic, and intergalactic medium. To exploit these observations, I am building an extensive forward-modeling framework that predicts the Lyα cosmic web and calibrates how it traces the underlying matter web of dark matter and galaxies. I will present predictions for the abundance and surface brightness of Lyα filaments and first results on recovering their gas, turning the large-scale Lyα emission into a quantitative probe of the baryonic cosmic web.