Emission lines of [O II] in the optical and ultraviolet spectra of planetary nebulae
Abstract
Recent R-matrix calculations of electron impact excitation rates in O II are used to calculate the emission-line ratio-ratio diagrams (R_1, R_2), (R_1, R_3) and (R_1, R_4), where R_1 = I(3729 A)/I(3726 A), R_2 = I(7320 A)/I(3726 + 3729 A), R_3 = I(7330 A)/I(3726 + 3729 A) and R_4 = I(2470 A)/I(3726 + 3729 A), for a range of electron temperatures (T_e = 7500-20 000 K) and electron densities (N_e = 10^1.5-10^5 cm^-3) appropriate to planetary nebulae. These diagrams should, in principle, allow the simultaneous determination of T_e and N_e from measurements of the [O II] emission lines in a spectrum. Plasma parameters deduced for a sample of planetary nebulae, using observational data obtained with the IUE satellite and the Hamilton Echelle spectrograph on the 3-m Shane Telescope at the Lick Observatory, are found to show excellent internal consistency, and to be in generally good agreement with the values of T_e and N_e estimated from other line ratios in the echelle spectra. These results provide observational support for the accuracy of the theoretical ratios, and hence the atomic data adopted in their derivation.
- Publication:
-
Monthly Notices of the Royal Astronomical Society
- Pub Date:
- March 1999
- DOI:
- 10.1046/j.1365-8711.1999.02275.x
- Bibcode:
- 1999MNRAS.304...27K
- Keywords:
-
- ATOMIC DATA;
- PLANETARY NEBULAE: GENERAL;
- ULTRAVIOLET: ISM