EDP Sciences
Free access
Volume 404, Number 2, June III 2003
Page(s) 545 - 556
Section Formation, structure and evolution of stars
DOI http://dx.doi.org/10.1051/0004-6361:20030466

A&A 404, 545-556 (2003)
DOI: 10.1051/0004-6361:20030466

Optical spectrum of the planetary nebula M 2-24

Y. Zhang1 and X.-W. Liu2

1  National Astronomical Observatories, Chinese Academy of Sciences, Beijing 100012, PR China
2  Department of Astronomy, Peking university, Beijing 100871, PR China

(Received 28 November 2002 / Accepted 20 March 2003 )

We have obtained medium-resolution, deep optical long-slit spectra of the bulge planetary nebula (PN) M 2-24 . The spectrum covers the wavelength range from 3610-7330 Å. Over two hundred emission lines have been detected. The spectra show a variety of optical recombination lines (ORLs) from C, N, O and Ne ions. The diagnostic diagram shows significant density and temperature variations across the nebula. Our analysis suggests that the nebula has a dense central emission core. The nebula was thus studied by dividing it into two regions: 1) a high ionization region characterized by an electron temperature of $T_{\rm e}=16\,300$ K and a density of $\log\,N_{\rm e}({\rm cm}^{-3}) = 6.3$; and 2) a low ionization region represented by $T_{\rm e}=11\,400$ K and $\log\,N_{\rm
e}({\rm cm}^{-3}) = 3.7$ . A large number of ORLs from C, N, O and Ne ions have been used to determine the abundances of these elements relative to hydrogen. In general, the resultant abundances are found to be higher than the corresponding values deduced from collisionally excited lines (CELs). This bulge PN is found to have large enhancements in two $\alpha$-elements, magnesium and neon.

Key words: ISM: abundances -- planetary nebulae: individual: M 2-24 -- ISM: lines and bands

Offprint request: Y. Zhang, zhangy@bac.pku.edu.cn

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