Broad emission-line shifts in quasars: An orientation measure for radio-quiet quasars?

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dc.contributor.authorRichards, GT
dc.contributor.authorBerk, DEV
dc.contributor.authorReichard, TA
dc.contributor.authorHall, PB
dc.contributor.authorSchneider, DP
dc.contributor.authorSubbaRao, M
dc.contributor.authorThakar, AR
dc.contributor.authorYork, DG
dc.date.accessioned2025-01-21T01:30:23Z
dc.date.available2025-01-21T01:30:23Z
dc.date.issued2002
dc.description.abstractUsing a sample of 3814 quasars from the Early Data Release of the Sloan Digital Sky Survey, we confirm that high-ionization, broad emission lines, such as C IV are significantly blueshifted with respect to low-ionization, broad emission lines, such as Mg II which are thought to be close to the systemic redshift. We examine the velocity shifts of the Mg II and C iv emission lines with respect to [O III and Mg II respectively. C iv emission-line peaks have a range of shifts from a redshift of 500 km s(-1) to blueshifts well in excess of 2000 km s(-1) as compared with Mg II We confirm previous results that suggest an anticorrelation between the shift of the C iv emission-line peak and the rest equivalent width of the C iv emission line. Furthermore, by creating composite quasar spectra as a function of C iv shift, we are able to study in detail the profiles of the line as a function of velocity shift. We find that the apparent shift of the C iv emission-line peak is not a shift so much as it is a lack of flux in the red wing for the composite with the largest apparent shift. This observation should strongly constrain models for the broad emission-line region in quasars. The emission-line blueshift and equivalent width of C iv are also discussed in light of the well-known anticorrelation between the equivalent width of C iv emission and continuum luminosity, otherwise known as the Baldwin effect. We further discuss the C iv emission-line shift as a function of other quasar properties, such as spectral index, radio and X-ray detection. We find a possible correlation between the C iv emission-line shifts and the radio properties of the quasars, which is suggestive of orientation as the cause of the C iv velocity shifts. Finally, we explore whether the C iv emission-line blueshifts correlate with the presence of broad absorption line absorption troughs or with narrow, associated absorption, and how these might be related to orientation.
dc.fuente.origenWOS
dc.identifier.issn0004-6256
dc.identifier.urihttps://repositorio.uc.cl/handle/11534/96729
dc.identifier.wosidWOS:000176272900001
dc.issue.numero1
dc.language.isoen
dc.pagina.final17
dc.pagina.inicio1
dc.revistaAstronomical journal
dc.rightsacceso restringido
dc.subjectline : formation
dc.subjectline : profiles
dc.subjectquasars : emission lines
dc.subjectquasars : general
dc.titleBroad emission-line shifts in quasars: An orientation measure for radio-quiet quasars?
dc.typeartículo
dc.volumen124
sipa.indexWOS
sipa.trazabilidadWOS;2025-01-12
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