Active Galaxies in the Sloan Digital Sky Survey III: from quasars to radio galaxies?

TL;DR

This study analyzes the spectroscopic and radio properties of various active galactic nuclei in the Sloan Digital Sky Survey, revealing links between black hole mass, star formation, and radio activity, and challenging traditional unified models.

Contribution

It provides new insights into the evolution of active galactic nuclei, emphasizing the role of black hole growth and star formation over simple orientation-based models.

Findings

More massive SMBHs host stronger radio jets.

Anti-correlation between line strength and radio power.

Evidence for evolution in AGN properties over time.

Abstract

In this third of a series of papers concerning active galaxies in the FIRST and Sloan Digital Sky Surveys, we analyze the spectroscopic and radio properties of a sample of narrow-line Active Galactic Nuclei (AGN), broad-line Seyfert I galaxies, and Quasars in the local universe in order to investigate the dependence of their activity on the mass, spin and accretion rates of the supermassive black holes (SMBH) residing at the centers of their host galaxies. We show that galaxies hosting more massive SMBH are more likely to power stronger and larger radio jets, and we show a strong anti-correlation between the strength of the lines of radio emitting galaxies and their radio power. Furthermore we show that the compactness of a jet is correlated with the epoch of the last episode of star-formation, suggesting a link between the presence of cold gas in a galaxy, the size of its SMBH and the radio and spectroscopic features of its AGN. We use our large statistical sample to test the expectations of unified models of AGN based on orientation. While confirming that Seyfert II galaxies and radio galaxies are significantly more extincted then Seyfert Is and nearby Quasars, we find several major inconsistencies with such a paradigm. In particular we show a strong difference in the [OIII],[OII] and [NII] luminosities for different spectroscopic classes, a result which argues in favor of an evolution of the broad and narrow line regions of active nuclei over time. We suggests that evolution, rather than orientation, may be the key element in shaping the properties of active nuclei, as also suggested by the results of high-redshift X-ray and radio surveys and we speculate on a model that may predict this kind of evolution.