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dc.contributor.authorDenney, K. D.
dc.contributor.authorHorne, Keith
dc.contributor.authorShen, Yue
dc.contributor.authorBrandt, W. N.
dc.contributor.authorHo, Luis C.
dc.contributor.authorPeterson, B. M.
dc.contributor.authorRichards, Gordon T.
dc.contributor.authorTrump, J. R.
dc.contributor.authorGe, J.
dc.identifier.citationDenney , K D , Horne , K , Shen , Y , Brandt , W N , Ho , L C , Peterson , B M , Richards , G T , Trump , J R & Ge , J 2016 , ' The Sloan Digital Sky Survey Reverberation Mapping Project : an investigation of biases in C iv emission line properties ' , Astrophysical Journal Supplement Series , vol. 224 , no. 2 .
dc.identifier.otherPURE: 244545599
dc.identifier.otherPURE UUID: dd1ad2e2-5047-41de-9032-884892f194c9
dc.identifier.otherBibtex: urn:994a3b743150fe183a07ebd0c383e56b
dc.identifier.otherScopus: 84978080591
dc.identifier.otherWOS: 000381013200001
dc.description.abstractWe investigate the dependence on data quality of quasar properties measured from the C iv emission line region at high redshifts. Our measurements come from 32 epochs of Sloan Digital Sky Survey Reverberation Mapping Project spectroscopic observations of 482 z > 1.46 quasars. We compare the differences between measurements made from the single-epoch (SE) and coadded spectra, focusing on the C iv λ1549 emission line because of its importance for studies of high-redshift quasar demographics and physical properties, including black hole masses. In addition to statistical errors increasing (by factors of ∼2–4), we find increasing systematic offsets with decreasing signal-to-noise ratio (S/N). The systematic difference (measurement uncertainty) in our lowest-S/N (<5) subsample between the SE and coadded spectrum (i) C iv equivalent width is 17 Å (31 Å), (ii) centroid wavelength is <1 Å (2 Å), and fractional velocity widths, Δ v/v, characterized by (iii) the line dispersion, σl, is 0.104 (0.12), and (iv) the mean absolute deviation (MAD) is 0.072 (0.11). These remain smaller than the 1σ measurement uncertainties for all subsamples considered. The MAD is found to be the most robust line-width characterization. Offsets in the C iv FWHM velocity width and the C iv profile characterized by FWHM/σl are only smaller than the statistical uncertainties when S/N > 10, although offsets in lower-S/N spectra exceed the statistical uncertainties by only a factor of ∼1.5 and may depend on the type of functional fit to the line. Characterizing the C iv line profile by the kurtosis is the least robust property investigated, as the median systematic coadded–SE measurement differences are larger than the statistical uncertainties for all S/N subsamples.
dc.relation.ispartofAstrophysical Journal Supplement Seriesen
dc.rights© 2016 The American Astronomical Society. All rights reserved. This work is made available online in accordance with the publisher’s policies. This is the final published version of the work, which was originally published at:
dc.subjectGalaxies: activeen
dc.subjectGalaxies: nucleien
dc.subjectQuasars: emission linesen
dc.subjectQuasars: generalen
dc.subjectQuasars: supermassive black holesen
dc.subjectQB Astronomyen
dc.subjectQC Physicsen
dc.titleThe Sloan Digital Sky Survey Reverberation Mapping Project : an investigation of biases in C iv emission line propertiesen
dc.typeJournal articleen
dc.description.versionPublisher PDFen
dc.contributor.institutionUniversity of St Andrews.School of Physics and Astronomyen
dc.description.statusPeer revieweden

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