The environment of AGNs and the activity degree of their surrounding galaxies^⋆

Institut für Astrophysik, Universität Göttingen, Friedrich-Hund Platz 1, 37077 Göttingen, Germany
e-mail: wkollat@astro.physik.uni-goettingen.de

Received: 29 September 2011
Accepted: 10 October 2012

Abstract

Aims. We present results of a comprehensive spectral study on the large-scale environment of active galactic nuclei (AGNs) based on Sloan Spectroscopic Survey data.

Methods. We analyzed the spectra of galaxies in the environment of AGN and other activity classes up to distances of 1 Mpc.

Results. The mean Hα and [O iii] λ5007 line luminosities in the environmental galaxies within a projected radius of 1 Mpc are highest around Seyfert 1 galaxies, with decreasing luminosities for Seyfert 2 and HII galaxies, and lowest for absorption line galaxies. Furthermore, there is a trend toward Hα and [OIII] luminosities in the environmental galaxies increasing as a function of proximity to the central emission line galaxies. There is another clear trend toward a neighborhood effect within a radius of 1000 kpc for the AGN and non-AGN types: Seyfert galaxies tend to have the highest probability of having another Seyfert galaxy in the neighborhood. HII galaxies tend to have the highest probability of having another HII galaxy in the neighborhood, etc. The number of companions within 1000 kpc is inversely correlated with the Hα, [O iii] λ5007, as well as with the continuum luminosities of the central galaxies, regardless of whether they are of Seyfert, HII, or absorption line types.