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Title:
The emission-line properties of low-redshift quasi-stellar objects
Authors:
Boroson, Todd A.; Green, Richard F.
Affiliation:
AA(Kitt Peak National Observatory, Tucson, AZ), AB(Kitt Peak National Observatory, Tucson, AZ)
Publication:
Astrophysical Journal Supplement Series (ISSN 0067-0049), vol. 80, no. 1, May 1992, p. 109-135. (ApJS Homepage)
Publication Date:
05/1992
Category:
Astrophysics
Origin:
STI
NASA/STI Keywords:
EMISSION SPECTRA, LINE SPECTRA, QUASARS, SEYFERT GALAXIES, ASTRONOMICAL SPECTROSCOPY, COMPUTATIONAL ASTROPHYSICS, PRINCIPAL COMPONENTS ANALYSIS, RED SHIFT, SKY SURVEYS (ASTRONOMY)
DOI:
10.1086/191661
Bibliographic Code:
1992ApJS...80..109B

Abstract

The present study obtains spectra covering the 4300-5700 wavelength region for all 87 QSOs in the BQS catalog having redshifts less than 0.5. A novel empirical technique which allows the measurement and subtraction of the many Fe II lines in this region is applied to these spectra. Measurements of the strengths of H-beta, forbidden O III 5007, and He 4686, and a 4D parameterization of the H-beta profile are combined with optical, radio, and X-ray continuum information from the literature to elucidate how these properties are related. It is concluded that the dominant source of variation in the observed properties of low-redshift QSOs is a physical parameter which balances Fe II excitation against the illumination of the narrow line region. It is argued that this property is not driven by external orientation, i.e., the viewing angle. A comparison of subsamples defined by their radio properties suggest that radio-quiet and radio-loud objects cannot be parallel sequences because there is a large deficit of radio-quiet analogs to the steep-spectrum QSOs.

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