A New Halo Density Profile for Galaxies

More precise measurements of galaxy clustering will be provided by the next generation of galaxy surveys such as DESI, WALLABY and SKA. To utilize this information to improve our understanding of the Universe, we need to accurately model the distribution of galaxies in their host dark matter halos. In this work we present a new halo density profile model for galaxies, which makes predictions for the positions of galaxies in the host halo, different to the widely adopted Navarro-Frenk-White (NFW) profile, since galaxies tend to be found more in the outskirts of halos (nearer the virial radius) than an NFW profile. The parameterised density profile model is fit and tested using the DarkSage semi-analytic model of galaxy formation. We find that our density profile model can accurately reproduce the halo occupation distribution and galaxy two-point correlation function of the DarkSage simulation. We also derive the analytic expressions for the circular velocity and gravitational potential energy for this density profile. We use the SDSS DR10 galaxy group catalogue to validate this halo density profile model. Compared to the NFW profile, we find that our model more accurately predicts the positions of galaxies in their host halo and the galaxy two-point correlation function.