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Astron. Astrophys. 346, 753-763 (1999)

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Spectra of planetary nebulae in NGC 5128 (Centaurus-A)

J.R. Walsh 1, N.A. Walton 2, G.H. Jacoby 3 and R.F. Peletier 4

1 Space Telescope European Co-ordinating Facility, European Southern Observatory, Karl-Schwarzschild-Strasse 2,
D-85748 Garching bei München, Germany (jwalsh@eso.org)
2 Royal Greenwich Observatory, Apartado 321, Santa Cruz de La Palma, E-38780 Tenerife, Spain (naw@ing.iac.es)
3 Kitt Peak National Observatory, National Optical Astronomy Observatory, Tucson, AZ 85726, USA (gjacoby@noao.edu) *
4 Department of Physics, University of Durham, South Road, Durham DH1 3LE, England (R.F.Peletier@dur.ac.uk)

Received 13 August 1998 / Accepted 6 April 1999


Low dispersion spectra have been obtained of five planetary nebulae in the elliptical galaxy NGC 5128 (Centaurus-A) from the catalogue of Hui et al. (1993b). The planetary nebulae (PN) cover a range of galactocentric radius from 7.9 to 17.7´ (8 to 18 Kpc). The spectra display typical emission lines of H I, He I, He II, [O III], [N II] and [S II] and appear very similar to high excitation planetary nebulae in the Galaxy. This implies that, from a stellar evolution viewpoint, there should be no peculiar effects introduced by considering the bright cut-off of the PN luminosity function for distance estimation. In particular the brightest PN detected in NGC 5128 is not spectroscopically unusual. One of the PN shows relatively strong He II and [N II] lines and the derived N/O ratio indicates that it may be a Type I nebula, considered to arise from a high mass progenitor star. Determinations of the oxygen abundance of the five PN shows a mean value 0.5 dex below solar. Given that NGC 5128 is an elliptical galaxy with a presumably metal rich stellar content, the low metallicities of the PN are unexpected, although a similar situation has been observed in the bulge of M 31.

Key words: galaxies: elliptical and lenticular, cD – galaxies: individual: NGC 5128 (Centaurus-A)

* Visiting Astronomer, Steward Observatory, University of Arizona, 933 N. Cherry Ave, Tucson, AZ 85721, USA

Send offprint requests to: J.R. Walsh

© European Southern Observatory (ESO) 1999

Online publication: June 17, 1999