Spatially-resolved line emission from radiation-hydrodynamics simulations of the Milky Way

Aaron Smith

Tuesday, Dec. 6th, 12:10CET

Nebular recombination lines can provide extensive information about star-forming galaxies in the local and high-redshift Universe. I will briefly present a Lyman continuum (LyC), Lyman-α (Lyα), and Balmer line (Hα and Hβ) Monte Carlo radiative transfer study with the COLT code of a high-resolution isolated Milky Way radiation-hydrodynamic simulation. The realistic framework includes stellar feedback, non-equilibrium thermochemistry accounting for molecular hydrogen, and dust grain evolution in a multiphase interstellar medium (Arepo-RT + SMUGGLE). Accurate LyC reprocessing to recombination emission requires modeling pre-absorption by dust, helium ionization, and anisotropic escape fractions as these reduce the available budget for line emission (<60%), impacting inferred star formation rates. I will focus on the spatial morphology, time variability, gas-phase structure, and spatial-spectral and viewing angle dependence of the emergent photons. The Hα and Hβ radial and vertical surface brightness profiles are in excellent agreement with observations of nearby galaxies. Balmer decrement dust corrections work well but dust scattering is also important. Finally, in our simulations diffuse ionized gas and extraplanar Hα emission is powered by LyC photons escaping HII regions and the disk, respectively.