The Clustering of Low‐Luminosity Active Galactic Nuclei

Abstract

Based on the Sloan Digital Sky Survey (SDSS) DR2 sample, we present amultiparameter analysis of the spatial clustering of nearby activegalactic nuclei (AGNs). Estimates of the redshift-space two-pointcorrelation function reveal that Seyferts are less clustered than normalgalaxies, while LINERs' clustering amplitude (s0) isconsistent with that of the parent galaxy population. This difference inclustering is not driven by the morphology-density relation, as colorsand concentration indices follow similar distributions. The fact thatobjects of given spectral types are clustered differently seemscorrelated with a variety of their physical properties, includingL[OI], L[OIII], the emitting gas densityne, and the obscuration level. LINERs, which exhibit highs0, show the lowest luminosities and obscuration levels, andrelatively low ne, suggesting that these objects harborrelatively massive black holes that are weakly active or inefficient intheir accretion, probably due to the insufficiency of their fuel supply.Seyfert galaxies, which have low s0, are very luminous andshow large ne, suggesting that their black holes are lessmassive but accrete quickly and efficiently enough to clearly dominatethe ionization. Star-forming galaxies, the H IIs, are weakly clustered;this trend can be understood as a consequence of both themorphology-density and star formation rate-density relations. Thespectral properties of the H II galaxies suggest, however, that theyhide in their centers, amid large amounts of obscuring material, blackholes of generally low mass whose activity remains relatively feeble.Our own Milky Way may be such a case.