THE PLANETARY NEBULA POPULATION OF M33 AND ITS METALLICITY GRADIENT: A LOOK INTO THE GALAXY'S DISTANT PAST

Journal Article · Fri May 01 04:00:00 EDT 2009 · Astrophysical Journal

DOI:https://doi.org/10.1088/0004-637X/696/1/729; COUNTRY OF INPUT: INTERNATIONAL ATOMIC ENERGY AGENCY (IAEA)· OSTI ID:21296192

Magrini, Laura ^[1]; Stanghellini, Letizia ^[2]; Villaver, Eva ^[3]

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1. Istituto Nazionale di Astrofisica, Osservatorio Astrofisico di Arcetri (Italy)
2. National Optical Astronomy Observatories, Tucson, AZ 85719 (United States)
3. Space Telescope Science Institute, Baltimore, MD 21218 (United States)

The planetary nebula (PN) population of M33 is studied via multifiber spectroscopy with Hectospec at the MMT. In this paper, we present the spectra of 102 PNe, whereas plasma diagnostic and chemical abundances were performed on the 93 PNe where the necessary diagnostic lines were measured. About 20% of the PNe are compatible with being Type I; the rest of the sample is the progeny of an old disk stellar population, with main sequence masses M < 3 M {sub sun} and ages t > 0.3 Gyr. By studying the elemental abundances of the PNe in the M33 disk, we were able to infer that (1) there is a tight correlation between O/H and Ne/H, broadly excluding the evolution of oxygen; (2) the average abundances of the {alpha}-elements are consistent with those of H II regions, indicating a negligible global enrichment in the disk of M33 from the epoch of the formation of the PN progenitors to the present time; and (3) the radial oxygen gradient across the M33 disk has a slope of -0.031 {+-} 0.013 dex kpc{sup -1}, in agreement, within the errors, with the corresponding gradient derived from H II regions. Our observations do not seem to imply that the metallicity gradient across the M33 disk has flattened considerably with time. We report also the discovery of a PN with Wolf-Rayet features, PN039, belonging the class of late [WC] stars.

• OSTI ID: 21296192
• Journal Information: Astrophysical Journal, Journal Name: Astrophysical Journal Journal Issue: 1 Vol. 696; ISSN ASJOAB; ISSN 0004-637X
• Country of Publication: United States
• Language: English

Related Subjects

99 GENERAL AND MISCELLANEOUS
ABUNDANCE
GALACTIC EVOLUTION
GALAXIES
OXYGEN
PLANETARY NEBULAE
SPECTROSCOPY
STARS