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Revisited Abundance Diagnostics in Quasars: Fe II/Mg II Ratios

Verner, E.; Bruhweiler, F.; Verner, D.; Johansson, Sveneric LU and Gull, T. (2003) In Astrophysical Journal 592(2). p.59-62
Abstract
Both the Fe II UV emission in the 2000-3000 Å region [Fe II(UV)]and resonance emission line complex of Mg II at 2800 Å areprominent features in quasar spectra. The observed Fe II(UV)/Mg IIemission ratios have been proposed as means to measure the buildup ofthe Fe abundance relative to that of the alpha-elements C, N, O, Ne,and Mg as a function of redshift. The current observed ratios show largescatter and no obvious dependence on redshift. Thus, it remainsunresolved whether a dependence on redshift exists and whether theobserved Fe II(UV)/Mg II ratios represent a real nucleosynthesisdiagnostic. We have used our new 830 level model atom for Fe<SUP>+</SUP>in photoionization calculations, reproducing the physical conditions inthe... (More)
Both the Fe II UV emission in the 2000-3000 Å region [Fe II(UV)]and resonance emission line complex of Mg II at 2800 Å areprominent features in quasar spectra. The observed Fe II(UV)/Mg IIemission ratios have been proposed as means to measure the buildup ofthe Fe abundance relative to that of the alpha-elements C, N, O, Ne,and Mg as a function of redshift. The current observed ratios show largescatter and no obvious dependence on redshift. Thus, it remainsunresolved whether a dependence on redshift exists and whether theobserved Fe II(UV)/Mg II ratios represent a real nucleosynthesisdiagnostic. We have used our new 830 level model atom for Fe<SUP>+</SUP>in photoionization calculations, reproducing the physical conditions inthe broad-line regions of quasars. This modeling reveals thatinterpretations of high values of Fe II(UV)/Mg II are sensitive not onlyto Fe and Mg abundance, but also to other factors such asmicroturbulence, density, and properties of the radiation field. We findthat the Fe II(UV)/Mg II ratio combined with Fe II(UV)/Fe II(optical)emission ratio, where Fe II(optical) denotes Fe II emission in 4000-6000Å band, can be used as a reliable nucleosynthesis diagnostic forthe Fe/Mg abundance ratios for the physical conditions relevant to thebroad-line regions of quasars. This has extreme importance for quasarobservations with the Hubble Space Telescope and also with the futureJames Webb Space Telescope. (Less)
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author
organization
publishing date
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Contribution to journal
publication status
published
subject
keywords
Atomic Processes, Line: Formation, Methods: Numerical, Galaxies: Quasars: Emission Lines
in
Astrophysical Journal
volume
592
issue
2
pages
59 - 62
publisher
University of Chicago Press
external identifiers
  • wos:000184408300002
  • scopus:0042918051
ISSN
0004-637X
DOI
10.1086/377571
language
English
LU publication?
yes
id
fa18155e-ef3b-4234-9c00-2cbf349f4f68 (old id 130515)
date added to LUP
2007-07-20 14:19:33
date last changed
2017-02-05 04:16:02
@article{fa18155e-ef3b-4234-9c00-2cbf349f4f68,
  abstract     = {Both the Fe II UV emission in the 2000-3000 Å region [Fe II(UV)]and resonance emission line complex of Mg II at 2800 Å areprominent features in quasar spectra. The observed Fe II(UV)/Mg IIemission ratios have been proposed as means to measure the buildup ofthe Fe abundance relative to that of the alpha-elements C, N, O, Ne,and Mg as a function of redshift. The current observed ratios show largescatter and no obvious dependence on redshift. Thus, it remainsunresolved whether a dependence on redshift exists and whether theobserved Fe II(UV)/Mg II ratios represent a real nucleosynthesisdiagnostic. We have used our new 830 level model atom for Fe&lt;SUP&gt;+&lt;/SUP&gt;in photoionization calculations, reproducing the physical conditions inthe broad-line regions of quasars. This modeling reveals thatinterpretations of high values of Fe II(UV)/Mg II are sensitive not onlyto Fe and Mg abundance, but also to other factors such asmicroturbulence, density, and properties of the radiation field. We findthat the Fe II(UV)/Mg II ratio combined with Fe II(UV)/Fe II(optical)emission ratio, where Fe II(optical) denotes Fe II emission in 4000-6000Å band, can be used as a reliable nucleosynthesis diagnostic forthe Fe/Mg abundance ratios for the physical conditions relevant to thebroad-line regions of quasars. This has extreme importance for quasarobservations with the Hubble Space Telescope and also with the futureJames Webb Space Telescope.},
  author       = {Verner, E. and Bruhweiler, F. and Verner, D. and Johansson, Sveneric and Gull, T.},
  issn         = {0004-637X},
  keyword      = {Atomic Processes,Line: Formation,Methods: Numerical,Galaxies: Quasars: Emission Lines},
  language     = {eng},
  number       = {2},
  pages        = {59--62},
  publisher    = {University of Chicago Press},
  series       = {Astrophysical Journal},
  title        = {Revisited Abundance Diagnostics in Quasars: Fe II/Mg II Ratios},
  url          = {http://dx.doi.org/10.1086/377571},
  volume       = {592},
  year         = {2003},
}