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J/ApJ/669/791 Variable quasar sample (Wilhite+, 2007)
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Beginning of ReadMe :J/ApJ/669/791 Quasar black hole masses (Wilhite+, 2007)
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The effect of variability on the estimation of quasar black hole masses.
Wilhite B.C., Brunner R.J., Schneider D.P., Vanden Berk D.E.
<Astrophys. J., 669, 791-800 (2007)>
=2007ApJ...669..791W
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ADC_Keywords: Active gal. nuclei ; QSOs ; Spectroscopy ; Ultraviolet
Keywords: galaxies: active - quasars: general - techniques: spectroscopic
Abstract:
We investigate the time-dependent variations of ultraviolet (UV) black
hole mass estimates of quasars in the Sloan Digital Sky Survey (SDSS).
From SDSS spectra of 615 high-redshift (1.69<z<4.75) quasars with
spectra from two epochs, we estimate black hole masses using a
single-epoch technique, which employs an additional, automated
night-sky line removal and relies on UV continuum luminosity and CIV
lambda1549 emission-line dispersion. Mass estimates show variations
between epochs at about the 30% level for the sample as a whole. We
determine that for our full sample, measurement error in the line
dispersion likely plays a larger role than the inherent variability in
terms of contributing to variations in mass estimates between epochs.
However, we use the variations in quasars with r-band spectral
signal-to-noise ratio greater than 15 to estimate that the
contribution to these variations from inherent variability is roughly
20%. We conclude that these differences in black hole mass estimates
between epochs indicate that variability does not make a large
contribution to the current factor of 2 scatter between mass estimates
derived from low- and high-ionization emission lines.