Emission Tomography of the Lyman-alpha Cosmic Web

Abstract

Deep observations of faint, extended Lyman-alpha (Lyα) emission are beginning to reveal diffuse hydrogen in the circumgalactic medium of galaxies and in their embedding cosmic filaments, opening a new window on the baryon cycle that links galaxies to their gaseous large-scale environment. I will review recent observations of diffuse Lyα emission and their proposed physical interpretations, highlighting key challenges and degeneracies in connecting them to the underlying gas distribution. I will then summarize recent advances in galaxy formation and Lyα radiative transfer simulations and discuss their implications for current and upcoming surveys with instruments such as MUSE, KCWI, VIRUS, and HSC. Finally, I will present first results from inference and reconstruction methods that connect simulations and observations of the Lyα cosmic web in emission, complementing similar efforts in recent tomographic Lyα forest absorption studies.