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The 15R-North galaxy redshift survey is a uniform spectroscopic survey (S/N ∼10) covering the range 3650—7400˚A for 3149 galaxies with median redshift 0.05. The sample is 90 % complete to R = 15.4. The median slit covering fraction is 24 % of the galaxy, apparently sufficient to minimize the effects of aperture bias on the EW(Hα). Forty-nine percent of the galaxes in the survey have one or more emission lines detected at ≥ 2σ. In agreement with previous surveys, the fraction of absorption-line galaxies increases steeply with galaxy luminosity. We use Hβ, O[III], Hα, and [N ii] to discriminate between star-forming galaxies and AGNs. At least 20 % of the galaxies are star-forming, at least 17 % have AGN-like emission, and 12 % have unclassifiable emission. The unclassified 12% may include a “hybrid ” population of galaxies with both star-formation and AGN activity. The AGN fraction increases steeply with luminosity; the fraction of star-forming galaxies decreases.
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Carter et al. (2001) studied this question.
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