The Close Environment of Seyfert Galaxies and Its Implication for Unification Models

This paper presents a statistical analysis of the circumgalactic environment of nearby Seyfert galaxies based on a computer-aided search of companion galaxies on the Digitized Sky Survey (DSS). An intrinsic difference between the environment of Seyfert 1 and Seyfert 2 galaxies, suggested by previous work, is confirmed as statistically significant. For Seyfert 2 galaxies we find a significant excess of large companions (diameter of companion >= 10 Kpc) within a search radius <= 100 Kpc of projected linear distance, as well as within a search radius equal to three times the diameter \ds of each Seyfert galaxy. For Seyfert 1 galaxies there is no clear evidence of any excess of companion galaxies neither within 100 Kpc, nor within 3\ds. For all samples the number of companions suggests a markedly non-Poissonian distribution for galaxies on scales <= 100 Kpc. This difference in environment is not compatible with the simplest formulation of the Unification Model for Seyferts: both types 1 and 2 should be intrinsicaly alike, the only difference being due to orientation of an obscuring torus. We propose an alternative formulation.