The environment of active objects in the nearby universe
Abstract
We study the galaxy environment of active galaxies, radio-loud and radio-quiet quasars in the redshift range 0.1≤ z≤0.25. We use APM galaxies in order to explore the local galaxy overdensity and the bJ-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 R=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 overdensity of radio-loud and radio-quiet quasars are comparable. The analysis of the distribution of bJ-R galaxy colour indexes suggests that the environment of quasars is not strongly dominated by a population of red galaxies, characteristic of rich Abell cluster, an effect that is more clearly appreciated for our sample of radio-loud quasars.
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