The environment of active objects in the nearby Universe

We study the galaxy environment of active galaxies, radio-loud and radio-quiet quasars in the redshift range 0.1 less than or equal toz less than or equal to 0.25. We use galaxies from the APM survey in order to explore the local galaxy overdensity and the b(J) - R colour distribution of neighbouring galaxies of these target samples. For comparison, we perform similar analysis on samples of Abell clusters with X-ray emission, and samples of Abell clusters with richness R = 1 and 0. The projected cross-correlations show that the samples of quasars and active galaxies reside in regions of galaxy density enhancements lower than those typical of R = 0 clusters. We also find that in the nearby Universe the local galaxy overdensities of radio-loud and radio-quiet quasars are comparable. The analysis of the distribution of b(J)-R galaxy colour indices suggests that the environment of quasars is not strongly dominated by a population of red galaxies, characteristic of rich Abell clusters, an effect that is more clearly appreciated for our sample of radio-loud quasars.