Abstract
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 4.2m WHT telescope (La Palma, Spain). Line intensities and logarithmic extinction, cβ, are presented for 42 objects. Their location in the Sabbadin & D'Odorico diagnostic diagram (H�/(S ii) vs H�/(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 4363u (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.
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