A model for halo formation with axion mixed dark matter

There are several issues to do with dwarf galaxy predictions in the standard CDM cosmology that have suscitated much recent debate about the possible modication of the nature of dark matter as providing a solution. We explore a novel solution involving ultra-light axions that can potentially resolve the missing satellites problem, the cusp-core problem, and the ‘too big to fail’ problem. We discuss approximations to non-linear structure formation in dark matter models containing a component of ultra-light axions across four orders of magnitude in mass, 10 24 eV . ma . 10 20 eV, a range too heavy to be well constrained by linear cosmological probes such as the CMB and matter power spectrum, and too light/non-interacting for other astrophysical or terrestrial axion searches. We nd that an axion of mass ma 10 21 eV contributing approximately 85% of the total dark matter can introduce a signicant kpc