The integrated spectra of nearby galaxies - General properties and emission-line spectra

Abstract

Results from a survey of the integrated spectra of 90 nearby galaxies are presented. Intermediate- and low-resolution spectrophotometry over the 3650-7000-A range is used to compile a spectral atlas of galaxies and to investigate the systematic behavior of the emission-line spectra in normal and peculiar galaxies. The integrated absorption- and emission-line spectra show a smooth progression with Hubble type. Most spiral and irregular galaxies exhibited detectable emission lines of H-alpha forbidden O II, N II, S II, and sometimes H-beta and forbidden O III. Methods for distinguishing between distant starburst galaxies and active nuclei are discussed. The new data are used to examine the statistical properties of the forbidden O II emission in galaxies and to calibrate a mean relation between O II luminosity and the total star formation rate. The forbidden O II distribution for faint galaxies is very similar to that which is observed for nearby Markarian galaxies.