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Abstract Weak emission-line quasars (WLQs) are a subset of type 1 quasars that exhibit extremely weak Lyα+ Nvλ1240 and/or Civλ1549 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 atz< 0.5 and 1.5 <z< 3.5 that have rest-frame ultraviolet and optical spectral measurements. We apply a correction to the Hβ-based black hole mass (MBH) estimates of these quasars using the strength of the optical Feiiemission. We confirm previous findings that WLQs’MBHvalues are overestimated by up to an order of magnitude using the traditional broad-emission-line region size–luminosity relation. With thisMBHcorrection, we find a significant correlation between Hβ-based Eddington luminosity ratios and a combination of the rest-frame Civequivalent width and Civblueshift with respect to the systemic redshift. This correlation holds for both ordinary quasars and WLQs, which suggests that the two-dimensional Civparameter space can serve as an indicator of accretion rate in all type 1 quasars across a wide range of spectral properties.
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Gemini Near Infrared Spectrograph–Distant Quasar Survey: Prescriptions for Calibrating UV-based Estimates of Supermassive Black Hole Masses in High-redshift Quasars
Abstract The most reliable single-epoch supermassive black hole mass (MBH) estimates in quasars are obtained by using the velocity widths of low-ionization emission lines, typically the Hβλ4861 line. Unfortunately, this line is redshifted out of the optical band atz≈ 1, leavingMBHestimates to rely on proxy rest-frame ultraviolet (UV) emission lines, such as Civλ1549 or Mgiiλ2800, which contain intrinsic challenges when measuring, resulting in uncertainMBHestimates. In this work, we aim at correctingMBHestimates derived from the Civand Mgiiemission lines based on estimates derived from the Hβemission line. We find that employing the equivalent width of Civin derivingMBHestimates based on Mgiiand Civprovides values that are closest to those obtained from Hβ. We also provide prescriptions to estimateMBHvalues when only Civ, only Mgii, and both Civand Mgiiare measurable. We find that utilizing both emission lines, where available, reduces the scatter of UV-basedMBHestimates by ∼15% when compared to previous studies. Lastly, we discuss the potential of our prescriptions to provide more accurate and precise estimates ofMBHgiven a much larger sample of quasars at 3.20 ≲z≲ 3.50, where both Mgiiand Hβcan be measured in the same near-infrared spectrum.
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- PAR ID:
- 10422167
- Publisher / Repository:
- DOI PREFIX: 10.3847
- Date Published:
- Journal Name:
- The Astrophysical Journal
- Volume:
- 950
- Issue:
- 2
- ISSN:
- 0004-637X
- Format(s):
- Medium: X Size: Article No. 96
- Size(s):
- Article No. 96
- Sponsoring Org:
- National Science Foundation
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