dc.contributor.author Coatman, Liam en dc.contributor.author Hewett, Paul en dc.contributor.author Banerji, Manda en dc.contributor.author Richards, GT en dc.contributor.author Hennawi, JF en dc.contributor.author Prochaska, JX en dc.date.accessioned 2017-01-24T10:03:55Z dc.date.available 2017-01-24T10:03:55Z dc.date.issued 2017-02-01 en dc.identifier.issn 0035-8711 dc.identifier.uri https://www.repository.cam.ac.uk/handle/1810/261989 dc.description.abstract The C $\small \text{IV}$λλ1498,1501 broad emission line is visible in optical spectra to redshifts exceeding $z$ ∼ 5. C $\small \text{IV}$ has long been known to exhibit significant displacements to the blue and these ‘blueshifts’ almost certainly signal the presence of strong outflows. As a consequence, single-epoch virial black hole (BH) mass estimates derived from C $\small \text{IV}$ velocity widths are known to be systematically biased compared to masses from the hydrogen Balmer lines. Using a large sample of 230 high-luminosity ($L_\text{Bol}$ = 10$^{45.5}$–10$^{48}$ erg s$^{-1}$), redshift 1.5 < $z$ < 4.0 quasars with both C $\small \text{IV}$ and Balmer line spectra, we have quantified the bias in C $\small \text{IV}$ BH masses as a function of the C $\small \text{IV}$ blueshift. C $\small \text{IV}$ BH masses are shown to be a factor of 5 larger than the corresponding Balmer-line masses at C $\small \text{IV}$ blueshifts of 3000 km s$^{-1}$ and are overestimated by almost an order of magnitude at the most extreme blueshifts, ≳5000 km s$^{-1}$. Using the monotonically increasing relationship between the C $\small \text{IV}$ blueshift and the mass ratio BH(C $\small \text{IV}$)/BH(H$\alpha$), we derive an empirical correction to all C $\small \text{IV}$ BH masses. The scatter between the corrected C $\small \text{IV}$ masses and the Balmer masses is 0.24 dex at low C $\small \text{IV}$ blueshifts (∼0 km s$^{-1}$) and just 0.10 dex at high blueshifts (∼3000 km s$^{-1}$), compared to 0.40 dex before the correction. The correction depends only on the C $\small \text{IV}$ line properties – i.e. full width at half-maximum and blueshift – and can therefore be applied to all quasars where C $\small \text{IV}$ emission line properties have been measured, enabling the derivation of unbiased virial BH-mass estimates for the majority of high-luminosity, high-redshift, spectroscopically confirmed quasars in the literature. dc.description.sponsorship LC thanks the Science and Technology Facilities Council (STFC) for the award of a studentship. PCH acknowledges support from the STFC via a Consolidated Grant to the Institute of Astronomy, Cambridge. MB acknowledges support from STFC via an Ernest Rutherford Fellowship. Funding for the SDSS and SDSS-II has been provided by the Alfred P. Sloan Foundation, the Participating Institutions, the National Science Foundation, the US Department of Energy, the National Aeronautics and Space Administration, the Japanese Monbukagakusho, the Max Planck Society and the Higher Education Funding Council for England. The SDSS website is http://www.sdss.org/. The SDSS is managed by the Astrophysical Research Consortium for the Participating Institutions. The Participating Institutions are the American Museum of Natural History, Astrophysical Institute Potsdam, University of Basel, University of Cambridge, Case Western Reserve University, University of Chicago, Drexel University, Fermilab, the Institute for Advanced Study, the Japan Participation Group, Johns Hopkins University, the Joint Institute for Nuclear Astrophysics, the Kavli Institute for Particle Astrophysics and Cosmology, the Korean Scientist Group, the Chinese Academy of Sciences (LAMOST), Los Alamos National Laboratory, the Max-Planck-Institute for Astronomy (MPIA), the Max-Planck-Institute for Astrophysics (MPA), New Mexico State University, Ohio State University, University of Pittsburgh, University of Portsmouth, Princeton University, the United States Naval Observatory and the University of Washington. 1iraf is distributed by the National Optical Astronomy Observatory, which is operated by the Association of Universities for Research in Astronomy (AURA) under a cooperative agreement with the National Science Foundation. dc.language eng en dc.language.iso en en dc.publisher Oxford University Press dc.subject galaxies: evolution en dc.title Correcting C $\small \text{IV}$-Based Virial Black Hole Masses en dc.type Article prism.endingPage 2142 prism.issueIdentifier 2 en prism.publicationDate 2017 en prism.publicationName Monthly Notices of the Royal Astronomical Society en prism.startingPage 2120 prism.volume 465 en dc.identifier.doi 10.17863/CAM.7233 dcterms.dateAccepted 2016-10-26 en rioxxterms.version VoR en rioxxterms.licenseref.uri http://www.rioxx.net/licenses/all-rights-reserved en rioxxterms.licenseref.startdate 2017-02-01 en dc.contributor.orcid Hewett, Paul [0000-0002-6528-1937] dc.contributor.orcid Banerji, Manda [0000-0002-0639-5141] dc.identifier.eissn 1365-2966 dc.publisher.url http://10.0.4.69/mnras/stw2797 en rioxxterms.type Journal Article/Review en pubs.funder-project-id SCIENCE & TECHNOLOGY FACILITIES COUNCIL (ST/N000927/1) cam.issuedOnline 2016-10-30 en dc.identifier.url http://10.0.4.69/mnras/stw2797 en
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