Local and Large-Scale Environment of Seyfert Galaxies

We present a three-dimensional study of the local (≤100 h-1 kpc) and the large-scale (≤1 h-1 Mpc) environment of the two main types of Seyfert AGN galaxies. For this purpose we use 48 Seyfert 1 galaxies (with redshifts in the range 0.007 ≤ z ≤ 0.036) and 56 Seyfert 2 galaxies (with 0.004 ≤ z ≤ 0.020), located at high galactic latitudes, as well as two control samples of nonactive galaxies having the same morphological, redshift, and diameter size distributions as the corresponding Seyfert samples. Using the Center for Astrophysics (CfA2) and Southern Sky Redshift Survey (SSRS) galaxy catalogs (mB ~ 15.5) and our own spectroscopic observations (mB ~ 18.5), we find that within a projected distance of 100 h-1 kpc and a radial velocity separation of δv 600 km s-1 around each of our AGNs, the fraction of Seyfert 2 galaxies with a close neighbor is significantly higher than that of their control (especially within 75 h-1 kpc) and Seyfert 1 galaxy samples, confirming a previous two-dimensional analysis of Dultzin-Hacyan et al. We also find that the large-scale environment around the two types of Seyfert galaxies does not vary with respect to their control sample galaxies. However, the Seyfert 2 and control galaxy samples do differ significantly when compared to the corresponding Seyfert 1 samples. Since the main difference between these samples is their morphological type distribution, we argue that the large-scale environmental difference cannot be attributed to differences in nuclear activity but rather to their different type of host galaxies.