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Excitation of emission lines by fluorescence and recombination in IC 418

Published online by Cambridge University Press:  30 August 2012

Vladimir Escalante ,
Cristophe Morisset  and
Leonid Georgiev
Vladimir Escalante
Affiliation:
CRyA, UNAM, Ap. Postal 72–3, C. P. 58091, Morelia, Michoacán, Mé[email protected]
Cristophe Morisset
Affiliation:
CRyA, UNAM, Ap. Postal 72–3, C. P. 58091, Morelia, Michoacán, Mé[email protected]
Leonid Georgiev
Affiliation:
Instituto de Astronomía, UNAM Ap. Postal 70–264, C. P. 04510, México, D. F., México emails: [email protected], [email protected]
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Abstract

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We predict intensities of lines of CII, NI, NII, OI and OII and compare them with a deep spectroscopic survey of IC 418 to test the effect of excitation of nebular emission lines by continuum fluorescence of starlight. Our calculations use a nebular model and a synthetic spectrum of its central star to take into account excitation of the lines by continuum fluorescence and recombination. The NII spectrum is mostly produced by fluorescence due to the low excitation conditions of the nebula, but many CII and OII lines have more excitation by fluorescence than recombination. In the neutral envelope, the NI permitted lines are excited by fluorescence, and almost all the OI lines are excited by recombination. Electron excitation produces the forbidden optical lines of OI, but continuum fluorescence excites most of the NI forbidden line intensities. Lines excited by fluorescence of light below the Lyman limit thus suggest a new diagnostic to explore the photodissociation region of a nebula.

Keywords

planetary nebulae: individual (IC 418)atomic processesradiation mechanisms: general
Type
Contributed Papers
Information
Proceedings of the International Astronomical Union , Volume 7 , Symposium S283: Planetary Nebulae: An Eye to the Future , July 2011 , pp. 350 - 351
Copyright
Copyright © International Astronomical Union 2012

References

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