Issue |
Astron. Astrophys. Suppl. Ser.
Volume 135, Number 3, March II 1999
|
|
---|---|---|
Page(s) | 437 - 466 | |
DOI | https://doi.org/10.1051/aas:1999183 | |
Published online | 15 March 1999 |
AGNs with composite spectra *,**
II. Additional data
Observatoire de Haute-Provence, CNRS, F-04870 Saint Michel l'Observatoire, France
Send offprint request to: A.C. Gonçalves
Received:
11
August
1998
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.
© European Southern Observatory (ESO), 1999