Local and nonlocal halo bias

Local and nonlocal halo bias

      In order to extract cosmological information from the galaxy surveys, the halo bias must be understood.  We extend the standard local bias to include the nonlocal effects. It is shown that large scale gravitational evolution naturally induces nonlocal corrections to the halo biasing prescription. The proposed nonlocal effects are measured in numerical simulations. We also develop a novel test of local bias, and argue that the smoothing scale in the local biasing prescription controls the scale at which the the prescription measures. By using a simple mapping, we demonstrate that local biasing prescription can be used to recover the original unsmoothed power spectrum rather well.