Abstract
In a sample of 476931 NELGs obtained from the SDSS DR5 data we find that in 22% of the galaxies the emission line [OIII]λ5007, Hβ, or both, are missing. The nature of the activity in these galaxies was determined using a diagnostic diagram comparing the equivalent width of [NII]λ6584 with the ratio [NII]λ6584/Hα. The majority of these galaxies are AGN. The Hα emission lines have a mean FWHM of 400 km s^{-1} and mean luminosity of 5.6×10^39 erg s^{-1}, which justify their classification as LLAGN. A study of their star formation histories using STARLIGHT reveals no trace of star formation over the last Gyr period. The hosts of the LLAGNs are early-type, T ≤ 2, with bulges more massive than those of the luminous AGNs.
