Description
I will present first results from the new Colibre simulations with a focus on atomic gas in galaxies. These simulations build on the successes of the EAGLE project with comprehensive changes to the treatment of cold gas in particular. Whereas many contemporary simulations impose a gas temperature floor around 10^4 K, in Colibre gas cools to ~10 K. Atomic and molecular hydrogen is modelled self-consistently via a state-of-the-art chemical network implementation including non-equilibrium effects for a subset of reactions including HI-H2. The model's predictions for HI properties of galaxies are remarkably well-converged with numerical resolution and only minimal resolution-dependent adjustments of model parameters. Early comparisons with the observed HI mass function, stellar mass - HI fraction relation, HI mass-size relation, HI velocity width function and other scaling relations offer encouragement that these simulations will be an excellent tool to interpret surveys of HI in galaxies.
