Inferring dark matter halo properties for HI-selected galaxies
Abstract
An important test of LCDM is the degree of consistency between dark matter halo properties measured using galaxy kinematics and their cosmologically expected values. Due to the observational expense in obtaining resolved kinematics, this is typically done for small, hand-selected galaxy samples such as SPARC. Here I instead take a statistical approach, presenting constraints on the dark matter halo mass and concentration of ~22,000 individual galaxies visible both in HI (from the ALFALFA survey) and optical light (from the SDSS). This is achieved by combining two Bayesian models: one for the HI line width using kinematic modelling, and the other for the galaxy’s total baryonic mass using the technique of inverse subhalo abundance matching. I discuss the relative constraining power on halo properties offered by these two probes, their consistency, and the information gain from their combination, which will allow future surveys such as SKA to greatly improve our knowledge of the galaxy-halo connection.