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Atomic Processes in Planetary Nebulae

Published online by Cambridge University Press:  26 May 2016

Sultana N. Nahar
Sultana N. Nahar*
Affiliation:
Department of Astronomy, The Ohio State University, Columbus, OH 43210, USA

Abstract

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A hot central star illuminating the surrounding ionized H II region usually produces very rich atomic spectra resulting from basic atomic processes: photoionization, electron-ion recombination, bound-bound radiative transitions, and collisional excitation of ions. Precise diagnostics of nebular spectra depend on accurate atomic parameters for these processes. Latest developments in theoretical computations are described, especially under two international collaborations known as the Opacity Project (OP) and the Iron Project (IP), that have yielded accurate and large-scale data for photoionization cross sections, transition probabilities, and collision strengths for electron impact excitation of most astrophysically abundant ions. As an extension of the two projects, a self-consistent and unified theoretical treatment of photoionization and electron-ion recombination has been developed where both the radiative and the dielectronic recombination processes are considered in an unified manner. Results from the Ohio State atomic-astrophysics group, and from the OP and IP collaborations, are presented. A description of the electronic web-interactive database, TIPTOPBASE, with the OP and the IP data, and a compilation of recommended data for effective collision strengths, is given.

Type
Part VI: The Ionized Gas in Planetary Nebulae
Information
Symposium - International Astronomical Union , Volume 209: Planetary Nebulae: Their Evolution and Role in the Universe , 2003 , pp. 325 - 334
Copyright
Copyright © Astronomical Society of the Pacific 2003 

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