The fraction of AGN in major merger galaxies and its luminosity
  dependence
  We use a phenomenological model which connects the galaxy and AGN populations
to investigate the process of AGN triggering through major galaxy mergers at
z~0. The model uses stellar mass functions as input and allows the prediction
of AGN luminosity functions based on assumed Eddington ratio distribution
functions (ERDFs). We show that the number of AGN hosted by merger galaxies
relative to the total number of AGN increases as a function of AGN luminosity.
This is due to more massive galaxies being more likely to undergo a merger and
does not require the assumption that mergers lead to higher Eddington ratios
than secular processes. Our qualitative analysis also shows that to match the
observations, the probability of a merger galaxy hosting an AGN and accreting
at a given Eddington value has to be increased by a factor ~10 relative to the
general AGN population. An additional significant increase of the fraction of
high Eddington ratio AGN among merger host galaxies leads to inconsistency with
the observed X-ray luminosity function. Physically our results imply that,
compared to the general galaxy population, the AGN fraction among merger
galaxies is ~10 times higher. On average, merger triggering does however not
lead to significantly higher Eddington ratios.
