A spectroscopic study of Planetary Nebulae in the Magellanic Clouds

• Main Author: Monk, David James
• Published: University College London (University of London) 1986
• Subjects: 520
• Online Access: http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.577469

Spectroscopic data for 74 Planetary Nebulae (PN) in the Large and Small Magellanic Clouds (LMC and SMC) have been analysed. The optical line fluxes have been used to determine the nebular temperatures and densities, and the abundances of He, N, 0, Ne, and Ar, relative to H. In the sample the analogues of Galactic PN are found: there are 5 (and possibly 10) He- and N-rich nebulae resembling Peimbert's Type I PN, 6 objects with low oxygen abundance, analogous to the PN of the Galactic Halo, 5 very-low-excitation (VLE) nebulae, and 5 PN central stars with Wolf-Rayet WC class features. Mean abundances are calculated for each cloud, from the nebulae not in the Type I, 'low-oxygen', or VLE groups, and are compared with the average abundances for Galactic PN, and H II regions in the Galaxy, the LMC, and the SMC. The comparison shows a significant enhancement of He and N in the LMC and SMC PN, with respect to LMC and SMC H II regions, whilst oxygen, neon, and argon abundances are similar in PN and H II regions within each galaxy. The central star luminosities and HI Zanstra temperatures are derived for 19 objects within the survey, and are compared to the evolutionary tracks for PN central stars of Schonberner (1979,1983). The comparison shows good agreement between theory and observation for most objects, although the high luminosity of LMC N201 (27502 L0 )places it a long way above the tracks. Of the six MC PN with low oxygen abundances two, LMC N25 and LMC N199, also have very low ionic helium abundances, and central star temperatures at which only a small contribution from neutral helium would be expected (40000 - 45000 K). LMC N25 is studied in more detail through the analysis of recent IPCS spectra.