The atomic-to-molecular hydrogen transition in the TNG50 simulation: Using realistic UV fields to create spatially resolved H <scp>i</scp> maps

Cold gas in galaxies provides a crucial test to evaluate the realism of cosmological hydrodynamical simulations. To extract atomic and molecular hydrogen properties simulated galaxy population, postprocessing methods taking local UV field into account are required. We improve upon previous studies by calculating realistic fields with dust radiative transfer code SKIRT model atomic-to-molecular transition TNG50, highest-resolution run IllustrisTNG suite. Comparing integrated quantities such as HI mass function, we study what detail needs be modelled order calculate cold properties. then new, spatially resolved comparisons for exploring synthetic maps at redshift zero compare them 21-cm observations from WHISP survey. In terms non-parametric morphologies, find that TNG50 less concentrated than their counterparts (median $\Delta C\approx0.3$), due part central deficits related ejective character supermassive black hole feedback TNG. column density distribution discrepancies between depend on total abundance these datasets well method. fully exploit synergy simulations upcoming deep HI/H2 data, advocate use accurate estimate radiation generate mock maps.