Speaker
Description
Lyman-$\alpha$ (Ly$\alpha$) emission is commonly produced through star formation or AGN activity, but in escaping its host galaxy, Ly$\alpha$ photons resonantly scatter off neutral hydrogen in the circumgalactic medium (CGM), thereby tracing both internal galaxy processes and the kinematics/composition of the surrounding gas. We model the diverse observed spatial and spectral shapes of the resulting Lyman-$\alpha$ halos (LAH). These halos connect to the baryonic cycle between feedback-driven outflows and the CGM, but also have critical observational effects: at a given intrinsic luminosity, different halos can be observed to different limiting fluxes. By inserting our model LAHs into VLT/MUSE observations, we study how detectability varies with halo configuration. We construct halo-dependent selection functions for 3 < z < 5 LAHs, recovering intrinsic distributions of key halo shape parameters. We apply our selection function to spectra of a mock Ly$\alpha$ population based on a simulated Ly$\alpha$-emitting galaxy, showing that star-formation-driven outflows are strongly associated with broad, red-peak-dominated Ly$\alpha$ lines, which are preferentially detected. We discuss how this influences detected LAH populations and their interpretations for galaxy evolution across cosmic time. Finally, we explore available data from JWST to relate observed host galaxy characteristics to halo shape distributions and outflow phase.