Statistics of QSO broad emission-line profiles. 2: The C IV wavelength 1549, C III) wavelength 1909, and MG II wavelength 2798 lines

Details Statistics of QSO broad emission-line profiles. 2: The C IV wavelength 1549, C III) wavelength 1909, and MG II wavelength 2798 lines Statistics of QSO broad emission-line profiles. 2: The C IV wavelength 1549, C III) wavelength 1909, and MG II wavelength 2798 lines

Mar 1994

adsabs.harvard.edu/cgi-bin/nph-data_query?bibcode=1994apj...423..131b&link_type=abstract

The Astrophysical Journal, Part 1 (ISSN 0004-637X), vol. 423, no. 1, p. 131-142

Astronomy and Astrophysics

Astrophysics

75

Carbon, Emission Spectra, Line Spectra, Magnesium, Quasars, Radio Galaxies, Kinematics, Radio Emission, Red Shift, Spectral Line Width

Scientific paper

We present the results of a statistical investigation of broad emission-line profiles in a sample of 85 intermediate redshift Quasi-Stellar Objects (QSOs) (primarily 0.9 less than or equal to z less than or equal to 2.2), split about equally between radio-loud and radio-quiet objects. These emission lines, from the spectra of Steidel & Sargent's Mg II wavelength 2798 absorption line survey, are reanalyzed in light of new results involving correlations with line width. Some new strong trends are found as line width (Full width at half-maximum (FWHM)) increases: the ratio of line peak to continuum intensity decreases for C III) wavelength 1909, the intensity ratio CIII) wavelength 1909/C IV wavelength 1549 increases, the intensity ratio C III) wavelength 1909/Mg II wavelength 2798 decreases, and the peaks of C III) wavelength 1909 and C IV wavelength 1549 become increasingly blueshifted relative to the Mg II wavelength 2798 peak. We present strong, clear differences between the broad emission-line spectra of radio-loud and radio-quiet QSOs. Radio-quiet objects have broader C III) wavelength 1909 and C IV wavelength 1549 lines than radio-loud objects, but the distributions of Mg II FWHMs do not differ significantly. The average ratio (FWHMC III)/(FWHMMg II) = 1.59 +/- 0.08 and (FWHMC IV)/(FWHMMg II) = 1.35 +/- 0.09 for radio-quiet objects, but both are consistent with unity (+/- 0.07) for radio-loud objects. The average ratio (FWHMC III)/(FWHMC IV) = 1.20 +/- 0.05 for both radio-loud and radio-quiet objects. We interpret these results in terms of the two-component profile: a narrow core (FWHM approximately 2000 km/s) and a broad base (FWHM approximately 7000 km/s) blueshifted by approximately 1000 km/s. The core-to-base ratio determines the FWHM, asymmetry, and line shift. In geneeral, radio-loud objects tend to have larger core-to-base ratios than radio-quiet objects. This scheme reproduces the observed correlations and most C IV wavelength 1549 and CIII) wavelength 1909 profiles reasonably well, although the broadest C III) lines (FWHMC III is greater than 7000 km/s, typically radio-quiet objects) require either a base component with a blueshift that increases with line width, or a third extremely broad component with a very large blueshift.

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