Echelle spectroscopy and photoionization modelling of the entire planetary nebula NGC 6210
Abstract
High-resolution spectroscopy of NGC 6210, show that recombination line abundances of O+2 and Ne+2 are two to three times larger than forbidden line abundances, Te(O+2) is smaller than Te(N+) and possibly Te(S+), the ionized mass is ≃0.07 M⊙ and the progenitor zero-age main-sequence mass is 1.2-2 M⊙. If electrons are in equilibrium, recombination lines are likely produced in a cold low-density medium. A photoionization model (cloudy 13.03) with a positive density gradient and two exciting sources, reproduced most of the optical spectrum, the temperature distribution of the nebula, He ii 4686/He i 5876, [O ii]3726/[O iii]5007 and [O ii]3726/3729, but not the other density sensitive line ratios. Including fluorescence and recombination, we found good agreement with observed C ii and C iii line intensities, O ii and O iii model intensities which are 2.6 and 7.8 times smaller than observed and large erratic differences with observations in C iii, N ii and N iii lines. UV and IR data suggest that [O ii] emission is from a region ∼ 6 times less dense than assumed by the model and that IR lines are produced in a medium where the density is ∼1000 cm-3. There may be a lower density medium beyond a dense ring described by the photoionization model, as well as a cold low-density component. A multicomponent model is required to reproduce the entire spectrum of NGC 6210.
- Publication:
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Monthly Notices of the Royal Astronomical Society
- Pub Date:
- February 2015
- DOI:
- 10.1093/mnras/stu2389
- Bibcode:
- 2015MNRAS.447..817B
- Keywords:
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- ISM: abundances;
- ISM: individual objects: NGC 6210