Variability Selected Active Galactic Nuclei from ASAS-SN Survey:
  Constraining the Low Luminosity AGN Population
  Low luminosity active galactic nuclei (LLAGN) probe accretion physics in the
low Eddington regime and can provide additional clues about galaxy evolution.
AGN variability is ubiquitous and thus provides a reliable tool for finding
AGN. We analyze the All-Sky Automated Survey for SuperNovae light curves of
1218 galaxies with $g<14$ mag and Sloan Digital Sky Survey spectra in search of
AGN. We find 37 objects that are both variable and have AGN-like structure
functions, which is about 3% of the sample. The majority of the variability
selected AGN are LLAGN with Eddington ratios ranging from $10^{-4}$ to
$10^{-2}$. We thus estimate the fraction of LLAGN in the population of galaxies
as 2% down to a median Eddington ratio of $2\times10^{-3}$. Combining the BPT
line ratio diagnostics and the broad-line AGN, up to $\sim$60% of the AGN
candidates are confirmed spectroscopically. The BPT diagnostics also classified
10-30% of the candidates as star forming galaxies rather than AGN.
