Induced nuclear activity in galaxy pairs with different morphologies
  (E+E), (E+S) and (S+S)
  We analysed 385 galactic spectra from the Sloan Digital Sky Survey Data
Release 7 (SDSS-DR7) that belong to the catalog of isolated pairs of galaxies
by Karachentsev. The spectra corresponds to physical pairs of galaxies as
defined by V $\leq$ 1200 Km/s and a pair separation $\leq$ 100 kpc. We search
for the incidence of nuclear activity, both thermal (star-forming) and
non-thermal -Active Galactic Nuclei (AGN). After a careful extraction of the
nuclear spectra, we use diagnostic diagrams and find that the incidence of AGN
activity is 48 \% in the paired galaxies with emission lines and 40\% for the
total sample (as compared to $\sim$ 43 \% and 41\% respectively in a sample of
isolated galaxies). These results remain after dissecting the effects of
morphological type and galactic stellar mass (with only a small, non
significant, enhancement of the AGN fraction in pairs of objects). These
results suggest that weak interactions are not necessary or sufficient to
trigger low-luminosity AGN. Since the fraction of AGN is predominant in early
type spiral galaxies, we conclude that the role of a bulge, and a large gas
reservoir are both essential for the triggering of nuclear activity. The most
striking result is that type 1 galaxies are almost absent from the AGN sample.
This result is in conflict with the Unified Model, and suggests that high
accretion rates are essential to form the Broad Line Region in active galaxies.
