Astron. Astrophys. Suppl. Ser.
Volume 135, Number 3, March II 1999
|Page(s)||437 - 466|
|Published online||15 March 1999|
II. Additional data
Observatoire de Haute-Provence, CNRS, F-04870 Saint Michel l'Observatoire, France
Send offprint request to: A.C. Gonçalves
Accepted: 17 November 1998
In a previous paper (Véron et al. 1997) we presented medium resolution (3.4 Å FWHM) spectroscopic observations of 15 "transition objects”, selected for having an ambiguous location in the Veilleux & Osterbrock (1987) diagnostic 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 HII region. Here, we report new spectroscopic observations of 53 emission-line galaxies with a "transition” spectrum, bringing 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 exist at all. By eliminating "composite objects” from the diagnostic diagrams, a clear separation between the different classes of nuclear emission-line regions (Seyfert 2s, Liners and HII regions) becomes apparent; by restricting the volume occupied by the different line-emitting regions in the 3-dimensional diagnostic diagrams, we are also restricting the range of possible physical parameters in these regions. There seems to be no continuity between Seyfert 2s and Liners, the two classes occupying distinct volumes in the 3-dimensional space defined by , , and .
Key words: galaxies: active / galaxies: nuclei / galaxies: seyfert
Based on observations collected at the Observatoire de Haute-Provence (CNRS), France, and Hubble Space Telescope (HST) data obtained from the Space Telescope European Coordinating Facility (ST-ECF) archive.
Tables 5 and 6 are also available in electronic form at the CDS via anonymous ftp to cdsarc.u-strasbg.fr (220.127.116.11) or via http://cdsweb.u-strasbg.fr/Abstract.html
© European Southern Observatory (ESO), 1999