A Possible Bias Model for Quasars

We propose that the majority of quasars at redshift $z\sim 1 - 5$ formed inthe environment of new born collapsed halos with 1-D velocity dispersion$\sigma_v^{1d} \sim 400 \kms$. The harboring coefficient $f$ of quasars perhalo and the lifetime of quasars depend only on local process, not modulated bythe density inhomogeneities on scales larger than the size of the halos. Thus,the bias of quasars on scale larger than the size of these halos is mainlydetermined by the parameter $\sigma_v$ used for quasar environmentidentification. With this model, the popular structure formation models, likeSCDM and LCDM, can be fairly well reconciled with the data of quasars,including a. observed feature of the environment for quasars; b. redshiftevolution of quasar abundance; c. the two-point correlation functions ofquasars. This bias model predicts that the correlation function of quasarsdoesn't significantly evolve, or only slightly increases with redshift.Comment: accepted for publication in ApJ Letters; 11 pages with 3 figures include