Optical spectrum of the planetary nebula M 2-24

Astrophysics, abstract
astro-ph/0304011

From: Yong Zhang <zhangy@vega.bac.pku.edu.cn>

Date: Tue, 1 Apr 2003 05:46:10 GMT   (81kb)

Authors:
Y. Zhang,
X.-W. Liu

Comments: 16 pages, 7 figures; accepted for publication in A&A

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 A. 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) an high ionization region characterized by an electron temperature
of T_e=16,300K and a density of logN_e(cm^{-3})=6.3; and 2) a low ionization
region represented by T_e=11,400K and logN_e(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.

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