NASA/IPAC EXTRAGALACTIC DATABASE
Date and Time of the Query: 2019-06-15 T16:17:21 PDT
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For refcode 2009ApJ...707.1334W:
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2009ApJ...707.1334W Estimating Black Hole Masses in Active Galactic Nuclei Using the Mg II {lambda}2800 Emission Line Wang, Jian-Guo; Dong, Xiao-Bo; Wang, Ting-Gui; Ho, Luis C.; Yuan, Weimin; Wang, Huiyuan; Zhang, Kai; Zhang, Shaohua; Zhou, Hongyan Abstract. We investigate the relationship between the linewidths of broad Mg II {lambda}2800 and H{beta} in active galactic nuclei (AGNs) to refine them as tools to estimate black hole (BH) masses. We perform a detailed spectral analysis of a large sample of AGNs at intermediate redshifts selected from the Sloan Digital Sky Survey, along with a smaller sample of archival ultraviolet spectra for nearby sources monitored with reverberation mapping (RM). Careful attention is devoted to accurate spectral decomposition, especially in the treatment of narrow-line blending and Fe II contamination. We show that, contrary to popular belief, the velocity width of Mg II tends to be smaller than that of H{beta}, suggesting that the two species are not cospatial in the broad-line region. Using these findings and recently updated BH mass measurements from RM, we present a new calibration of the empirical prescriptions for estimating virial BH masses for AGNs using the broad Mg II and H{beta} lines. We show that the BH masses derived from our new formalisms show subtle but important differences compared to some of the mass estimators currently used in the literature. Key words: black hole physics, galaxies: active, quasars: emission lines, quasars: general
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