AGNs with composite spectra II. Additional data

In a previous paper (Veron et al. 1997) We presented medium resolution (3.4 Angstrom FWHM) spectroscopic observations of 15 "transition objects", sele cted for having an ambiguous location in the Veilleux & Osterbrock (1987) d iagnostic diagrams: and showed that most of them were in fact ''composite'' , this being due to the simultaneous presence on the slit of both a Seyfert or Liner nucleus and a H II region. Here, we report new spectroscopic obse rvations of 53 emission-line galaxies with a "transition" spectrum, bringin g up to 61 the total number of observed objects in an unbiased sample of 88 "transition objects" Almost all of the observed galaxies have a "composite " nature, confirming the finding that true "transition" spectra may not exi st at all. By eliminating "composite objects" from the diagnostic diagrams, a clear se paration between the different classes of nuclear emission-line regions (Se yfert 2s, Liners and H II regions) becomes apparent; by restricting the vol ume occupied by the different line-emitting regions in the S-dimensional di agnostic diagrams; we are also restricting the range of possible physical p arameters in these regions. There seems to be no continuity between Seyfert 2s and Liners, the two classes occupying distinct volumes in the 3-dimensi onal space defined by lambda 5007/H beta, lambda 6583/H alpha, and lambda 6 300/H alpha.