Revealing the Cosmic Web-dependent Halo Bias

Halo bias is the one of the key ingredients of the halo models. It was shown at a given redshift to be only dependent, to the first order, on the halo mass. In this study, four types of cosmic web environments—clusters, filaments, sheets, and voids—are defined within a state-of-the-art high-resolution N-body simulation. Within these environments, we use both halo-dark matter cross correlation and halo-halo autocorrelation functions to probe the clustering properties of halos. The nature of the halo bias differs strongly between the four different cosmic web environments described here. With respect to the overall population, halos in clusters have significantly lower biases in the ${10}^{11.0}\sim {10}^{13.5}{h}^{-1}{M}_{\odot }$ mass range. In other environments, however, halos show extremely enhanced biases up to a factor 10 in voids for halos of mass $\sim {10}^{12.0}{h}^{-1}{M}_{\odot }$. Such a strong cosmic web environment dependence in the halo bias may play an important role in future cosmological and galaxy formation studies. Within this cosmic web framework, the age dependency of halo bias is found to be only significant in clusters and filaments for relatively small halos $\lesssim {10}^{12.5}{h}^{-1}{M}_{\odot }$.