The Activity of the Neighbours of Seyfert Galaxies
  We present a follow-up study on a series of papers concerning the role of
close interactions as a possible triggering mechanism of AGN activity. We have
already studied the close (<100kpc/h) and the large scale (<1 Mpc/h)
environment of a local sample of Sy1, Sy2 and bright IRAS galaxies (BIRG) and
their respective control samples. The results led us to the conclusion that a
close encounter appears capable of activating a sequence where an absorption
line galaxy (ALG) galaxy becomes first a starburst, then a Sy2 and finally a
Sy1. Here we investigate the activity of neighboring galaxies of different
types of AGN, since both galaxies of an interacting pair should be affected. To
this end we present the optical spectroscopy and X-ray imaging of 30
neighbouring galaxies around two local (z<0.034) samples of 10 Sy1 and 13 Sy2
galaxies. Based on the optical spectroscopy we find that more than 70% of all
neighbouring galaxies exhibit star forming and/or nuclear activity (namely
recent star formation and/or AGN), while an additional X-ray analysis showed
that this percentage might be significantly higher. Furthermore, we find a
statistically significant correlation, at a 99.9% level, between the value of
the neighbour's [OIII]/H\beta ratio and the activity type of the central active
galaxy, i.e. the neighbours of Sy2 galaxies are systematically more ionized
than the neighbours of Sy1s. This result, in combination with trends found
using the Equivalent Width of the H\alpha emission line and the stellar
population synthesis code STARLIGHT, indicate differences in the stellar mass,
metallicity and star formation history between the samples. Our results point
towards a link between close galaxy interactions and activity and also provide
more clues regarding the possible evolutionary sequence inferred by our
previous studies.
