The Activity of the Neighbours of AGN and Starburst Galaxies: Towards an
  evolutionary sequence of AGN activity
  We present a follow-up study of a series of papers concerning the role of
close interactions as a possible triggering mechanism of the activity of AGN
and starburst (SB) galaxies. We have already studied the close (<100 kpc) and
the large scale (<1 Mpc) environment of Sy1, Sy2 and Bright IRAS galaxies and
their respective control samples (Koulouridis et al.). The results led us to
the conclusion that a close encounter appears capable of activating a sequence
where a normal galaxy becomes first a starburst, then a Sy2 and finally a Sy1
galaxy. However since both galaxies of an interacting pair should be affected,
we present here optical spectroscopy and X-ray imaging of the neighbouring
galaxies around our Seyfert and BIRG galaxy samples. We find that more than 70%
of all neighbouring galaxies exhibit thermal or/and nuclear activity (namely
enhanced star formation, starbursting and/or AGN) and furthermore we discovered
various trends regarding the type and strength of the neighbour's activity with
respect to the activity of the central galaxy, the most important of which is
that the neighbours of Sy2 are systematically more ionized, and their straburst
is younger, than the neighbours of Sy1s. Our results not only strengthen the
link between close galaxy interactions and activity but also provide more clues
regarding the evolutionary sequence inferred by previous results.
