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Shedding New Light on Weak Emission-line Quasars in the C iv–Hβ Parameter Space


Abstract Weak emission-line quasars (WLQs) are a subset of Type 1 quasars that exhibit extremely weak Ly$\alpha +$N V $\lambda$1240 and/or C IV $\lambda$1549 emission lines. We investigate the relationship between emission-line properties and accretion rate for a sample of 230 `ordinary' Type 1 quasars and 18 WLQs at $z < 0.5$ and $1.5 < z < 3.5$ that have rest-frame ultraviolet and optical spectral measurements. We apply a correction to the H$\beta$-based black-hole mass ($M_{\rm BH}$) estimates of these quasars using the strength of the optical Fe II emission. We confirm previous findings that WLQs' $M_{\rm BH}$ values are overestimated by up to an order of magnitude using the traditional broad emission-line region size-luminosity relation. With this $M_{\rm BH}$ correction, we find a significant correlation between H$\beta$-based Eddington luminosity ratios and a combination of the rest-frame C IV equivalent width and C IV blueshift with respect to the systemic redshift. This correlation holds for both ordinary quasars and WLQs, which suggests that the two-dimensional C IV parameter space can serve as an indicator of accretion rate in all Type 1 quasars across a wide range of spectral properties.
Authors Trung Ha ORCID , Cooper Dix ORCID , Brandon M. Matthews ORCID , Ohad Shemmer ORCID , Michael S. Brotherton University of WyomingORCID , Adam D. Myers University of Wyoming , Gordon T. Richards ORCID , Jaya Maithil ORCID , Scott F. Anderson ORCID , W. N. Brandt ORCID , Aleksandar M. Diamond‐Stanic , Xiaohui Fan ORCID , S. C. Gallagher ORCID , Richard F. Green ORCID , P. Lira ORCID , B. Luo ORCID , H. Netzer ORCID , Richard M. Plotkin ORCID , Jessie C. Runnoe ORCID , Donald P. Schneider ORCID , Michael A. Strauss ORCID , Benny Trakhtenbrot ORCID , Jianfeng Wu ORCID
Journal Info IOP Publishing | The Astrophysical Journal , vol: 950 , iss: 2 , pages: 97 - 97
Publication Date 6/1/2023
ISSN 0004-637X
TypeKeyword Image article
Open Access gold Gold Access
DOI https://doi.org/10.3847/1538-4357/acd04d
KeywordsKeyword Image Gravitational Lensing (Score: 0.481173)