A possible bias model for quasars

We propose that the majority of quasars at redshift z similar to 1-5 formed in the environment of newborn collapsed halos with one-dimensional velocity dispersion sigma(v)(1d) similar to 400 km s(-1). The harboring coefficient f of quasars per halo and the lifetime of quasars depend only on local processes; they are not modulated by the density inhomogeneities on scales larger than the size of the halos. Thus, the bias of quasars on scales larger than the size of these halos is mainly determined by the parameter sigma(v), which is used for quasar environment identification. With this model, the popular structure formation models, like the standard cold dark matter (SCDM) and the low-velocity CDM, can be fairly well reconciled with the data of quasars, including (1) observed features of the environment for quasars, (2) the redshift evolution of quasar abundance, and (3) the two-point correlation functions of quasars. This bias model predicts that the correlation function of quasars does not significantly evolve or only slightly increases with redshift.