Atomic data from the Iron Project. XLIV. Transition probabilities and line ratios for Fe VI with fluorescent excitation in planetary nebulae
Abstract
Relativistic atomic structure calculations for electric dipole (E1), electric quadrupole (E2) and magnetic dipole (M1) transition probabilities among the first 80 finestructure levels of Fe VI, dominated by configurations 3d^{3}, 3d^{2}4s, and 3d^{2}4p, are carried out using the BreitPauli version of the code SUPERSTRUCTURE. Experimental energies are used to improve the accuracy of these transition probabilities. Employing the 80level collisionradiative (CR) model with these dipole and forbidden transition probabilities, and Iron Project Rmatrix collisional data, we present a number of [Fe VI] line ratios applicable to spectral diagnostics of photoionized H II regions. It is shown that continuum fluorescent excitation needs to be considered in CR models in order to interpret the observed line ratios of optical [Fe VI] lines in planetary nebulae NGC 6741, IC 351, and NGC 7662. The analysis leads to parametrization of line ratios as function of, and as constraints on, the electron density and temperature, as well as the effective radiation temperature of the central source and a geometrical dilution factor. The spectral diagnostics may also help ascertain observational uncertainties. The method may be generally applicable to other objects with intensive background radiation fields, such as novae and active galactic nuclei. The extensive new Iron Project radiative and collisional calculations enable a consistent analysis of many line ratios for the complex iron ions. The complete tables of transition probabilities are only available in electronic form at the CDS via anonymous ftp to cdsarc.ustrasbg.fr (130.79.128.5) or via http://cdsweb.ustrasbg.fr/Abstract.html.
 Publication:

Astronomy and Astrophysics Supplement Series
 Pub Date:
 November 2000
 DOI:
 10.1051/aas:2000365
 arXiv:
 arXiv:astroph/0003410
 Bibcode:
 2000A&AS..147..111C
 Keywords:

 ATOMIC DATA;
 LINE FORMATION;
 STARS: WHITE DWARFS;
 ISM: H II REGIONS: PLANETARY NEBULAE;
 Astrophysics;
 Physics  Atomic Physics
 EPrint:
 25 pages, 8 figures, submitted to Astron.Astrophys. Suppl.Ser