TY  - JOUR
SP  - 47
VL  - 273
PB  - BLACKWELL SCIENCE LTD
A1  - LIU, XW
A1  - BARLOW, MJ
A1  - DANZIGER, IJ
A1  - CLEGG, RES
JF  - Monthly Notices of the Royal Astronomical Society
Y1  - 1995/03//
UR  - https://doi.org/10.1093/mnras/273.1.47
ID  - discovery10096154
N2  - The temperature-sensitive neutral carbon forbidden lines at 8727, 9824 and 9850 ? have been measured simultaneously for the first time from a planetary nebula. The nebulae NGC 2346, NGC 2440, NGC 3132 and IC 4406 were observed. Accurate rest wavelengths of these lines are obtained. The observed line ratios I(?9824+?9850)/I(?8727) are consistent with collisional excitation by electron impacts. It is demonstrated that radiative recombination and stellar continuum fluorescence are unimportant in exciting the observed [CI] lines, with the possible exception of NGC 2440 where a contribution from the former process cannot be ruled out. For NGC 2346, NGC 3132 and IC 4406, the observed [C I]line ratios yield electron temperatures between 7400 and 8000 K, about 1800 to 2800 K lower than those deduced from the [N II], [S III] and [O III] line ratios that we also measured. Electron densities are derived from the observed [N I], [S II] and [Cl III] doublet ratios.
N1  - This version is the version of record. For information on re-use, please refer to the publisher?s terms and conditions.
KW  - line formation
KW  -  planetary nebulae: general
AV  - public
TI  - Neutral carbon far-red forbidden line emission from planetary nubulae
SN  - 0035-8711
EP  - 58
IS  - 1
ER  -