Assembly bias, galactic conformity, and the galaxy-halo connection
The halo model of galaxy evolution assumes all properties of a galaxy are determined statistically by the mass of its host halo. While this assumption yields predictions that largely agree with observations, the full picture of the galaxy-halo connection is incomplete without assembly bias. Halo assembly bias refers to the dependence of present-day halo clustering on factors besides mass, such as a halo's age and assembly history, and is predicted by cosmological simulations. Probes of galaxy assembly bias include galactic conformity and the differential clustering of star-forming and quiescent central galaxies at fixed stellar mass. In this talk I will explain why two-halo galactic conformity is likely not a real effect, and demonstrate that efforts to refine galaxy evolution models should instead focus on correlations between halo accretion rate and galaxy properties like star formation rate. I will also show why observers should utilize mock galaxy surveys based on empirical models to correct for systematic errors and get the most out of existing galaxy surveys.