2008/01/14 by Robert Williams, Edward B. Jenkins, Jack A. Baldwin +4 · 1 voice · 22 citations
Physics and Astronomy · #Absorption (acoustics) #Astronomy and Astrophysical Research #Astrophysics and Star Formation Studies #Emission spectrum #Excited state #Forbidden mechanism #Ion #Line (geometry) #Recombination #Spectral line #Stars #Stellar, planetary, and galactic studies #astro-ph
paper · pdf · doi:10.1086/529065
published in The Astrophysical Journal 677(2), 1100-1119 (IOP Publishing) · 19 pages, 13 figures, accepted by ApJ. Preprint utilizes emulateapj.cls v. 12/01/06 (included)
arxiv created 2008/01/14 · arxiv published 2008/01/14 · arxiv updated 2008/01/14 · openalex publication_date 2008/04/11 · openalex created_date 2016/06/24 · openalex updated_date 2026/08/05
Emission-line abundances have been uncertain for more than a decade due to unexplained discrepancies in the relative intensities of the forbidden lines and weak permitted recombination lines in PNe and H II regions. The observed intensities of forbidden and recombination lines originating from the same parent ion differ from their theoretical values by factors of more than an order of magnitude in some of these nebulae. In this study we observe UV resonance line absorption in the central stars of PNe produced by the nebular gas and from the same ions that emit optical forbidden lines. We then compare the derived absorption column densities with the emission measures determined from ground-based observations of the nebular forbidden lines. We find for our sample of PNe that the collisionally excited forbidden lines yield column densities that are in basic agreement with the column densities derived for the same ions from the UV absorption lines. A similar comparison involving recombination line column densities produces poorer agreement, although near the limits of the formal uncertainties of the analyses. An additional sample of objects with larger abundance discrepancy factors will need to be studied before a stronger statement can be made that recombination line abundances are not correct.