Strong [O III] objects among sdss broad-line active galaxies

Randi R. Ludwig, Beverley Wills, Jenny E. Greene, Edward L. Robinson

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15 Scopus citations


We present the results of a spectral principal component analysis on 9046 broad-line active galactic nuclei from the Sloan Digital Sky Survey. We examine correlations between spectral regions within various eigenspectra (e.g., between Fe II strength and Hβ width) and confirm that the same trends are apparent in spectral measurements, as validation of our technique. Because we found that our sample had a large range in the equivalent width of [O III] λ5007, we divided the data into three subsets based on [O III] strength. Of these, only in the sample with the weakest equivalent width of [O III] were we able to recover the known correlation between [O III] strength and full width at half maximum of Hβ and their anticorrelation with Fe II strength. At the low luminosities considered here (L 5100Å of 1042- 1046 erg s-1), interpretation of the principal components is considerably complicated particularly because of the wide range in [O III] equivalent width. We speculate that variations in the covering factor are responsible for this wide range in [O III] strength.

Original languageEnglish (US)
Pages (from-to)995-1007
Number of pages13
JournalAstrophysical Journal
Issue number2
StatePublished - Dec 1 2009

All Science Journal Classification (ASJC) codes

  • Astronomy and Astrophysics
  • Space and Planetary Science


  • Active galaxies
  • Emission lines
  • Galaxies
  • Nuclei quasars


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