The nearby optical galaxy sample: The local galaxy luminosity function

In this paper we derive the galaxy luminosity function from the nearby opti cal galaxy (NOG) sample, which is a nearly complete, magnitude-limited (B l ess than or equal to 14 mag), all-sky sample of nearby optical galaxies (si milar to 6400 galaxies with cz < 5500 km s(-1)). For this local sample, we use galaxy distance estimates based on different peculiar velocity models. Therefore, the derivation of the luminosity function is carried out using t he locations of held and grouped galaxies in real distance space. The local held galaxy luminosity function in the B system is well described by a Sch echter function with a slope of alpha similar to -1.1, a low normalization factor (Phi* similar to 0.006 Mpc(-3)), and a particularly bright character istic magnitude (M-B* similar to -20.6) (H-0 = 75 km(-1) Mpc(-1)). The exac t values of the Schechter parameters depend slightly on the adopted peculia r velocity held models. Peculiar motion effects are of the order of statist ical errors and cause at most variations of 0.08 in alpha and 0.2 mag in M- B*. Our M-B* value is brighter by a few tenths of a magnitude than previous corresponding values, because using total corrected blue magnitudes better represent the galaxy light. In addition, the selection function, evaluated in terms of the luminosity function, appears to be not very sensitive to t he adopted peculiar velocity field models, which, however, have a large imp act on the local galaxy density on the smallest scales. The shape of the lu minosity function of spiral galaxies does not differ significantly from tha t of E-S0 galaxies;On the other hand, the late-type spirals and irregulars have a very steeply rising luminosity function toward the faint end (alpha similar to -2.3 to -2.4), whereas the ellipticals appreciably decrease in n umber toward low luminosities. The presence of galaxy systems in the NOG sa mple does not significantly affect the field galaxy luminosity function, si nce environmental effects on the total luminosity function appear to be mar ginal. The luminosity function of the members of the richest galaxy systems tends to show a slightly brighter M-B* value than the norm. In light of co nstraints imposed by the observed galaxy number counts, the low normalizati on of the luminosity function suggests that the nearby universe (cz less th an or similar to 5000 km s(-1)) examined in this paper may be underdense by a factor of similar to 1.5.