Abstract

Contributed Talk - Plenary

Probing Galactic Winds with Lyman Alpha Observables

Ole Wittig, Max Grönke, Chris Byrohl
Astronomisches Recheninstitut (ARI) Heidelberg

Galactic winds are one of the primary mechanisms by which galaxies regulate their own star formation and redistribute metals into the circumgalactic medium. Observationally, the Lyman-alpha (Lya) emission line is among the most accessible diagnostics of these winds: it is the brightest UV line in astrophysics, it traces neutral hydrogen directly, and its resonant nature makes it sensitive to the kinematics, column density, and geometry of outflowing gas in galactic winds. In theory, all of this information is encoded in the shape of the emerging spectrum. In practice, however, we lack a systematic understanding of how to decipher it, because multiple physical parameters shape the line profile in complex and correlated ways. My talk will focus on this degeneracy problem. Using radiative transfer simulations of outflowing shell models, I systematically study how individual gas properties such as column density, temperature, outflow velocity, and dust content alter the emerging Lya spectrum. To identify and characterise degeneracies between parameters, I employ a gradient-based sensitivity analysis of the spectra, revealing which combinations of physical conditions produce indistinguishable line profiles. Understanding these degeneracies is an important step toward making Lya a reliable and quantitative probe of galactic winds.