Evidence for a warm ISM in Fornax dEs - II. FCC032, FCC206 and FCCB729

Abstract

We present R-band and H-alpha+[N II] narrow-band imaging of FCC032, FCC206 and FCCB729, three dwarf elliptical galaxies (dEs) in the Fornax Cluster. These dEs contain significant amounts of ionized gas. FCC032 harbours a large ionized gas complex, consisting of several individual clouds, a superbubble and a filament that extends away from the galaxy centre. The ionized gas structures observed in FCC032 bear a strong resemblance to those observed in more gas-rich and more fiercely star-forming dwarf galaxies. FCC206, a very low surface brightness dE, contains one faint extended emission region, and two compact clouds. In FCCB729, the only nucleated galaxy in this sample, one of the ionized gas clouds coincides with the stellar nucleus. We derive ionized gas masses of a few 100 to 1000 solar masses for these galaxies. This brings our sample of dEs with ionized gas with H-alpha+[N II] narrow-band imaging to five objects. The ionized gas morphologies in these galaxies range from pure nuclear emission peaks to extended emission complexes. This morphological diversity could also indicate a diversity in ionizing processes in dEs with a warm interstellar medium (active galactic nuclei, starbursts, post-AGB stars,...). Inside FCC206, four star clusters appear to be on the verge of merging to form a nucleus in this presently non-nucleated dE. Understanding the formation of nuclei in dEs could give us important clues to the formation of super-massive black holes.