Luminosity function of galaxies in the nearby universe: The low-luminosityend of the nuclear activity sequence

We present an estimate of the shape of the luminosity functions in the near by Universe for the 4 types of extragalactic nuclear activity cited in Ho e t al. (1997a, AAA 68.158.311), i.e., H II, LINER, Transition, and Seyfert g alaxies, based on a magnitude limited complete sample of objects selected f rom the same work. This sample includes quite weaker nuclear emission objec ts than considered in previous studies, which has allowed us to assess the low-luminosity ends of the nuclear activity sequence for each type. It is f ound that three of the classes (LINER, Transition, and Seyferts) have very similar luminosity function shapes, and basically seem to differ only in th e relative numbers. HII objects tend to be found in different hosts (lower luminosity galaxies) and seem to have a bimodal luminosity function, with a fairly large proportion of Irr and dwarf galaxies in this class, which are superposed to a more Schechter-like luminosity function. Several observati onal properties also suggest that Transition objects are actually LINERs co ntaminated by H Ir regions, and should be included in that category. Our fi ts further suggest the presence of a substantial number of low-luminosity h ost Seyferts in the nearby Universe. The distribution of absolute magnitude s for Seyferts type 1 and 2 is very similar in our sample. The possibility that the LINER class encompasses several different classes of objects is al so discussed.