Measurements of the angular momentum-mass relations in the SIMBA simulation

We present measurements of the specific angular momentum content (j) of galaxies drawn from the SIMBA cosmological hydrodynamic simulations. For the stellar, H I and baryonic matter components we demonstrate the existence of extremely tight relations between j and the mass contained within the radius at which the H I mass surface density decreases to 1 M⊙ pc^-2. These relations are broadly consistent with a variety of empirical measurements. We confirm the observational result that the scatter in the stellar j- M relation is driven largely by H I content, and measure the dependence of its scatter on the deviations of galaxies from other important scaling relations. For a given stellar mass, H I-rich/poor galaxies have more/less-than-average stellar specific angular momentum. A similar, yet weaker, correlation exists for H I mass fraction. Overall, our results demonstrate the utility of the SIMBA simulations as a platform for understanding and contextualising the data and results from forthcoming large galaxy surveys.