LYα Absorber Correlations and the “Bias” of the LYα Forest

Abstract

Lyα absorber correlations contain information about the underlying density distribution associated with a particular class of absorbers. As such, they provide an opportunity to independently measure the “bias” of the Lyman alpha forest, i.e., the relationship between HI column density and underlying dark matter density. In these proceedings we use hydrodynamic simulations to investigate whether the evolution of this bias is measurable from observable correlations. Unfortunately, the increasingly complex physics in the IGM at z ≲ 1 makes a direct measurement of the bias difficult. Nevertheless, current simulations do make predictions for HI absorber correlations that are in broad agreement with observations at both high and low redshift, thus reinforcing the bias evolution predictions given by these models.