E. Koulouridis, M. Plionis, V. Chavushyan, D. Dultzin, Y. Krongold, I. Georgantopoulos, J. Leon-Tavares
We present a follow-up study on a series of papers concerning the role of
close interactions as a possible triggering mechanism of the activity of AGN
and starburst galaxies. We have already studied the close (< 100 kpc/h) and the
large scale (< 1 Mpc/h) environment 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 a normal
galaxy becomes first a starburst, then a Sy2 and finally a Sy1. 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
original Seyfert and BIRG galaxy samples. Based on optical spectroscopy we find
that more than 70% of all neighbouring galaxies exhibit thermal or/and nuclear
activity (namely enhanced star formation, starbursting and/or AGN), while an
additional X-ray analysis showed that this percentage can reach up to 100%.
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 galaxies are
systematically more ionized than the neighbours of Sy1s, a fact that indicates
differences in metallicity, stellar mass and star-formation history between the
samples. Our results not only strengthen the link between close galaxy
interactions and activity, but also provide more clues regarding the
evolutionary sequence inferred by our previous studies.
View original:
http://arxiv.org/abs/1111.4084
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