Quasars and Active Galactic Nuclei in Rich Environments. III. The Rapid Evolution of Active Galactic Nucleus Activity in Rich Clusters
Abstract
The evolution of optical activity in radio-loud quasars and low- redshift radio galaxies in different galaxian environments is analyzed using data available in the literature. For any given luminosity function (LF) and its evolution, an envelope model of the distribution of points in the absolute magnitude-redshift plane can be constructed which predicts the expected loci of the brightest objects observable at different redshift. By applying such models to the distribution of optical nuclear luminosities from the active component of quasars and radio galaxies as a function of redshift, it is found that objects in similar environments from both classes can be described by a single optical LF and evolution law. Furthermore, the high-luminosity end of the LF and evolution for the active galactic nucleus component of the combined sample of radio-loud quasars and radio galaxies situated in poor environments is consistent with that of optically selected quasars. Quasars situated in rich galaxy clusters, however, are found to evolve ~5 times faster than their counterparts in poorer environments. The extrapolation of this rapid evolution is also consistent with the level of optical activity found in radio galaxies in rich clusters at low redshift. This suggests that radio galaxies can be considered as current- epoch low-luminosity counterparts to radio-loud quasars. This evolution scenario can account for the earlier finding that only the least active objects are found in rich environments at low redshifts; whereas at z ~0.6, extremely bright quasars are found in rich clusters. The rapid evolution of quasars in rich clusters is likely to be connected to the evolution of the physical conditions in the clusters. This rapid evolution, however does not extrapolate to redshifts higher than z~0.7, implying a drastic change in the evolution rate at this epoch. This may indicate a decrease in the cluster formation rate or a saturation effect in the quasar LF.
- Publication:
-
The Astrophysical Journal
- Pub Date:
- July 1993
- DOI:
- 10.1086/172806
- Bibcode:
- 1993ApJ...411...43Y
- Keywords:
-
- Active Galactic Nuclei;
- Galactic Clusters;
- Galactic Evolution;
- Quasars;
- Radio Galaxies;
- Interacting Galaxies;
- Luminosity;
- Red Shift;
- Astrophysics;
- GALAXIES: ACTIVE;
- GALAXIES: CLUSTERING;
- GALAXIES: EVOLUTION;
- GALAXIES: NUCLEI;
- GALAXIES: QUASARS: GENERAL;
- RADIO CONTINUUM: GALAXIES