How to Reconcile the Observed Velocity Function of Galaxies with Theory

Within a Λ cold dark matter (ΛCDM) scenario, we use high-resolution cosmological simulations spanning over four orders of magnitude in galaxy mass to understand the deficit of dwarf galaxies in observed velocity functions (VFs). We measure velocities in as similar a way as possible to observations, including generating mock H i data cubes for our simulated galaxies. We demonstrate that this apples-to-apples comparison yields an “observed” VF in …