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Journal article
THE SLOAN DIGITAL SKY SURVEY REVERBERATION MAPPING PROJECT: AN INVESTIGATION OF BIASES IN C iv EMISSION LINE PROPERTIES
The Astrophysical journal. Supplement series, v 224(2), pp 14-14
26 May 2016
Abstract
ABSTRACT We 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 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, , characterized by (iii) the line dispersion, l, is 0.104 (0.12), and (iv) the mean absolute deviation (MAD) is 0.072 (0.11). These remain smaller than the 1 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/ l 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.
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Details
- Title
- THE SLOAN DIGITAL SKY SURVEY REVERBERATION MAPPING PROJECT: AN INVESTIGATION OF BIASES IN C iv EMISSION LINE PROPERTIES
- Creators
- K. D Denney - The Ohio State UniversityKeith Horne - University of St AndrewsYue Shen - National Center for Supercomputing Applications, University of Illinois at Urbana-Champaign, Urbana, IL 61801, USAW. N Brandt - Pennsylvania State UniversityLuis C Ho - Peking UniversityB. M Peterson - The Ohio State UniversityGordon T Richards - Drexel UniversityJ. R Trump - Pennsylvania State UniversityJ Ge - University of Florida Health
- Publication Details
- The Astrophysical journal. Supplement series, v 224(2), pp 14-14
- Publisher
- The American Astronomical Society
- Number of pages
- 15
- Resource Type
- Journal article
- Language
- English
- Academic Unit
- Physics
- Web of Science ID
- WOS:000381013200001
- Scopus ID
- 2-s2.0-84978080591
- Other Identifier
- 991019168283104721
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- Collaboration types
- Domestic collaboration
- International collaboration
- Web of Science research areas
- Astronomy & Astrophysics