OHP Preprint No. 96 : AGNs with composite spectra


AGNs with composite spectra

P. Veron (1), A. C. Gonšalves (1,2), M.-P. Veron (1)

(1) Observatoire de Haute-Provence (CNRS),
F-04870 Saint Michel l'Observatoire, France

(2) Centro de Astrofisica da Universidade do Porto,
Rua do Campo Alegre 823, 4150 Porto, Portugal

Abstract
The use of the Baldwin et al. (1981) or Veilleux & Osterbrock (1987) diagnostic diagrams allows the unambiguous classification of the nuclear emission line regions of most galaxies into one of three categories: nuclear HII regions or starbursts, Seyfert 2 galaxies and Liners. However, a small fraction of them have a "transition" spectrum. We present spectral observations of 15 "transition" objects at high-dispersion (66 ┼/mm around the H, [NII] 6548,6584 and/or H, [OIII] 4959,5007 emission lines. We show that most of these spectra are composite, due to the simultaneous presence on the slit of a Seyfert nucleus and a HII region. Seyfert 2s and Liners seem to occupy relatively small and distinct volumes in the three-dimensional space 5007/ H, 6584/H, 6300/H.

keywords : Galaxies: nuclei -- Galaxies: active


Astronomy & Astrophysics : submitted August 1996
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