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dc.contributor.authorCoatman, Liamen
dc.contributor.authorHewett, Paulen
dc.contributor.authorBanerji, Mandaen
dc.contributor.authorRichards, GTen
dc.contributor.authorHennawi, JFen
dc.contributor.authorProchaska, JXen
dc.date.accessioned2017-01-24T10:03:55Z
dc.date.available2017-01-24T10:03:55Z
dc.date.issued2017-02-01en
dc.identifier.issn0035-8711
dc.identifier.urihttps://www.repository.cam.ac.uk/handle/1810/261989
dc.description.abstractThe 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.sponsorshipLC 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.languageengen
dc.language.isoenen
dc.publisherOxford University Press
dc.subjectgalaxies: evolutionen
dc.titleCorrecting C $\small \text{IV}$-Based Virial Black Hole Massesen
dc.typeArticle
prism.endingPage2142
prism.issueIdentifier2en
prism.publicationDate2017en
prism.publicationNameMonthly Notices of the Royal Astronomical Societyen
prism.startingPage2120
prism.volume465en
dc.identifier.doi10.17863/CAM.7233
dcterms.dateAccepted2016-10-26en
rioxxterms.versionVoRen
rioxxterms.licenseref.urihttp://www.rioxx.net/licenses/all-rights-reserveden
rioxxterms.licenseref.startdate2017-02-01en
dc.contributor.orcidHewett, Paul [0000-0002-6528-1937]
dc.contributor.orcidBanerji, Manda [0000-0002-0639-5141]
dc.identifier.eissn1365-2966
dc.publisher.urlhttp://10.0.4.69/mnras/stw2797en
rioxxterms.typeJournal Article/Reviewen
pubs.funder-project-idSCIENCE & TECHNOLOGY FACILITIES COUNCIL (ST/N000927/1)
cam.issuedOnline2016-10-30en
dc.identifier.urlhttp://10.0.4.69/mnras/stw2797en


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