NGC 4286 AND NGC 3377A - GALAXIES WITH MIXED MORPHOLOGIES BETWEEN THE DWARF IM AND DE/DSO TYPES

Optical and radio data for the nucleated dwarf galaxy NGC 4286 show a mixed morphology between a star-forming Im type and a gas-poor dS0, N early-type dwarf. The Im dwarf NGC 3377A shows no gas depletion, but its morphology and size are similar to the "huge, very low surface brightness" (VLSB) gas-poor galaxies recently identified in the Virgo cluster. We interpret the morphology of NGC 4286 as an original Im system that has transformed itself (specification along the dwarf sequence) into a gas-poor dS0, N by losing most (but not all) of its original gas through an internal supergalactic wind that was generated earlier by a superluminous star cluster. The remnant of this cluster has now sunk to the center by dynamical friction to form the observed unresolved bright nucleus. Such star clusters and superwinds are known to exist in many present-day starburst Sm and amorphous galaxies such as NGC 1569 and NGC 1705.