EDP Sciences
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Volume 400, Number 2, March III 2003
Page(s) 511 - 520
Section Stellar clusters and associations
DOI http://dx.doi.org/10.1051/0004-6361:20030031

A&A 400, 511-520 (2003)
DOI: 10.1051/0004-6361:20030031

Spectroscopy of planetary nebulae in M 33

L. Magrini1, M. Perinotto1, R. L. M. Corradi2 and A. Mampaso3

1  Dipartimento di Astronomia e Scienza dello Spazio, Universitá di Firenze, L.go E. Fermi 2, 50125 Firenze, Italy
2  Isaac Newton Group of Telescopes, Apartado de Correos 321, 38700 Santa Cruz de La Palma, Canarias, Spain
3  Instituto de Astrofísica de Canarias, c. Vía Láctea s/n, 38200, La Laguna, Tenerife, Canarias, Spain

(Received 7 August 2002 / Accepted 29 November 2002 )

Spectroscopic observations of 48 emission-line objects of M 33 have been obtained with the multi-object, wide field, fibre spectrograph AF2/WYFFOS at the 4.2 m WHT telescope (La Palma, Spain). Line intensities and logarithmic extinction, $c_{\beta}$, are presented for 42 objects. Their location in the Sabbadin & D'Odorico diagnostic diagram (H $\alpha$/ [S II] vs. H $\alpha$/[N II]) suggests that >70% of the candidates are Planetary Nebulae (PNe). Chemical abundances and nebular physical parameters have been derived for the three of the six  PNe where the 4363 Å [O III] emission line was measurable. These are disc PNe, located within a galactocentric distance of 4.1 kpc, and, to date, they are the farthest PNe with a direct chemical abundance determination. No discrepancy in the helium, Oxygen and Argon abundances has been found in comparison with corresponding abundances of PNe in our Galaxy. Only a lower limit to the sulphur abundance has been obtained since we could not detect any [S III] line. N/H appears to be lower than the Galactic value; some possible explanations for this under-abundance are discussed.

Key words: planetary nebulae: individual: M 33 -- galaxies: individual: M 33 -- galaxies: abundances

Offprint request: L. Magrini laura@arcetri.astro.it

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