L-GALAXIES 2020: Spatially resolved cold gas phases, star formation and
  chemical enrichment in galactic discs
  We have updated the Munich galaxy formation model, L-Galaxies, to follow the
radial distributions of stars and atomic and molecular gas in galaxy discs. We
include an H2-based star-formation law, as well as a detailed
chemical-enrichment model with explicit mass-dependent delay times for SN-II,
SN-Ia and AGB stars. Information about the star formation, feedback and
chemical-enrichment histories of discs is stored in 12 concentric rings. The
new model retains the success of its predecessor in reproducing the observed
evolution of the galaxy population, in particular, stellar mass functions and
passive fractions over the redshift range 0<=z<=3 and mass range
8<=log(M_*/Msun)<=12, the black hole-bulge mass relation at z=0, galaxy
morphology as a function of stellar mass and the mass-metallicity relations of
both stellar and gas components. In addition, its detailed modelling of the
radial structure of discs allows qualitatively new comparisons with
observation, most notably with the relative sizes and masses of the stellar,
atomic and molecular components in discs. Good agreement is found with recent
data. Comparison of results obtained for simulations differing in mass
resolution by more than two orders of magnitude shows that all important
distributions are numerically well converged even for this more detailed model.
An examination of metallicity and surface-density gradients in the stars and
gas indicates that our new model, with star formation, chemical enrichment and
feedback calculated self-consistently on local disc scales, reproduces some but
not all of the trends seen in recent many-galaxy IFU surveys.
