Quasar-galaxy and AGN-galaxy cross-correlations

We compute quasar-galaxy and AGN-galaxy cross-correlation functions for sam ples taken from the Veron-Cetty & Veron catalog of quasars and active galax ies, using tracer galaxies taken from the Edinburgh/Durham Southern Catalog . The sample of active galaxy targets shows positive correlation at project ed separations r(p) <6 h(-1) Mpc consistent with the usual power law. On th e other hand, we do not find a statistically significant positive quasar-ga laxy correlation signal except in the range 3 h(-1) Mpc < r(p) < 6 h(-1) Mp c, where we find similar AGN-galaxy and quasar-galaxy correlation amplitude s. At separations r(p) < 3 h(-1) Mpc, a strong decline of quasar-galaxy cor relations is observed, suggesting a significant local influence of quasars in galaxy formation. In an attempt to reproduce the observed crosscorrelati on between quasars and galaxies, we have performed cold dark matter cosmolo gical hydrodynamic simulations and tested the viability of a scenario based on the model developed by Silk & Rees. In this scheme a fraction of the en ergy released by quasars is considered to be transferred into the baryonic component of the intergalactic medium in the form of winds. The results of the simulations suggest that the shape of the observed quasar-galaxy cross- correlation function could be understood in a scenario where a substantial amount of energy is transferred to the medium at the redshift of maximum qu asar activity.