AMIGA project: Active galaxies in a complete sample of isolated galaxies
  The project AMIGA (Analysis of the interstellar Medium of Isolated GAlaxies)
provides a statistically significant sample of the most isolated galaxies in
the northern sky. Such a control sample is necessary to understand the role of
the environment in evolution and galaxy properties like the interstellar medium
(ISM), star formation and nuclear activity. The data is publicly released under
a VO interface at http://amiga.iaa.es/. One of our main goals is the study of
nuclear activity in non-interacting galaxies using different methods. We focus
on the well known radiocontinuum-far infrared (FIR) correlation in order to
findradio-excess galaxies which are candidates to host an active galactic
nucleus (AGN) and FIR colours to find obscured AGN candidates. We looked for
the existing information on nuclear activity in the V\'eron-Cetty catalogue and
in the NASA Extragalactic Database (NED). We also used the nuclear spectra from
the Sloan Digital Sky Survey which allow us to determine the possible presence
of an AGN and to study the properties of the underlying stellar populations. We
produced a final catalogue of AGN-candidate galaxies which will provide a
baseline for the study of the nuclear activity depending on the environment. We
find that the fraction of FIR selected AGN-candidates ranges between 7% and
20%. There are no radio-excess galaxies in our sample above a factor 5 of radio
excess which is the lowest rate found in comparison with other samples in
denser environments. Finally, we obtained a fraction of about 22% of AGN using
the optical spectra, a significant fraction for a sample of isolated galaxies.
We conclude that the environment plays a crucial and direct role in triggering
radio nuclear activity and not only via the density-morphology or the
density-luminosity relations.
