Studies of the Virgo Cluster - Part Five - Luminosity Functions of Virgo Cluster Galaxies

The luminosity functions of galaxies of various Hubble types in the central 6° radius core of the Virgo cluster show fundamentally different forms for the high- and low-surface-brightness systems. The classical E, S0, and all of the spiral types have luminosity functions that are closely Gaussian, bounded at both the bright and faint limits, similar to what was originally proposed by Hubble. Dwarf ellipticals have an ever-increasing differential luminosity function to the completeness limit of our data at BT = 18 (MBT = - 13.7) which, when corrected for the known incompleteness to BT = 20(MBT = - 11.7), is similar to the exponential LF proposed by Zwicky. There are no dwarf spirals. Nucleated dE's exist at all magnitudes, but their percentage relative to the total dE population decreases with decreasing absolute luminosity of the parent. Gauss and Schechter LF's are fitted to the data, variously binned by Hubble types. The E and dE functions do not fit together, suggesting separate families with no continuity between them, contrary to the continuity displayed by certain integrated physical parameters (Paper I). The total luminosity of all supposed member galaxies in the central 6° core is 2.4 X 1012 blue solar luminosities. The luminosity density averaged over the 6° core is 5.6 x 1010 LBsun Mpc-3, which is 615 times larger than the mean luminosity density of the base4evel "homogeneous" universe.