Distribution of ionized gas in the nuclei of spiral galaxies

Narrow-band digital images have been obtained for a sample of spiral galaxies selected to contain low-ionization emission regions in their nuclei. The images have been processed to yield pure Hα+[N ii] images. These show that the optically emitting gas is usually concentrated in a nearly spherical core of half-intensity diameter typically 200 pc, often surrounded by a disk, in the galactic plane, traceable over a 600--900 pc diameter. This gas disk is not present in several cases in which it is expected by comparison with others of similar luminosity in emission, showing that some morphological variety exists among these emission regions