Abstract
A study of the distribution of ionized gas in the nuclear regions of a statistically significant sample of 91 non-Seyfert spirals is reported. CCD interference band images isolating the bright emission-lines of Hα + [N II] {lambda]λ6548, 6583 have been used to map the distribution of ionized gas in the inner 1-2 kpc of these galaxies. The galaxies exhibit a rich variety of nuclear and circumnuclear emission-line structures ranging from no detectable emission to bright stellar nuclei with complicated circumnuclear emission regions extending for many kiloparsecs. Trends with Hubble type and low-ionization nuclear emission-line spectral type (LINER or H II region) have been discerned. In galaxies with nuclear H II regions, those regions are on average the brightest H II regions in their host galaxies. It appears that nonthermal nuclear activity and nuclear star formation prefer different nuclear environments, with active nuclei tending to be found in intermediate-type galaxies, and nuclear H II regions preferring late-type spirals. It is speculated that this preference may be related to the dynamical properties of the host galaxies.
Published Version
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