Gemini Near Infrared Spectrograph-Distant Quasar Survey: Prescriptions for Calibrating UV-based Estimates of Supermassive Black Hole Masses in High-redshift Quasars

Cooper Dix, Brandon Matthews, Ohad Shemmer, Michael S. Brotherton, Adam D. Myers, I. Andruchow, W. N. Brandt, Gabriel A. Ferrero, Richard Green, Paulina Lira, Richard M. Plotkin, Gordon T. Richards, Donald P. Schneider

Research output: Contribution to journalArticlepeer-review

3 Scopus citations


The most reliable single-epoch supermassive black hole mass (M BH) estimates in quasars are obtained by using the velocity widths of low-ionization emission lines, typically the Hβ λ4861 line. Unfortunately, this line is redshifted out of the optical band at z ≈ 1, leaving M BH estimates to rely on proxy rest-frame ultraviolet (UV) emission lines, such as C iv λ1549 or Mg ii λ2800, which contain intrinsic challenges when measuring, resulting in uncertain M BH estimates. In this work, we aim at correcting M BH estimates derived from the C iv and Mg ii emission lines based on estimates derived from the Hβ emission line. We find that employing the equivalent width of C iv in deriving M BH estimates based on Mg ii and C iv provides values that are closest to those obtained from Hβ. We also provide prescriptions to estimate M BH values when only C iv, only Mg ii, and both C iv and Mg ii are measurable. We find that utilizing both emission lines, where available, reduces the scatter of UV-based M BH estimates by 15% when compared to previous studies. Lastly, we discuss the potential of our prescriptions to provide more accurate and precise estimates of M BH given a much larger sample of quasars at 3.20 ≲ z ≲ 3.50, where both Mg ii and Hβ can be measured in the same near-infrared spectrum.

Original languageEnglish (US)
Article number96
JournalAstrophysical Journal
Issue number2
StatePublished - Jun 1 2023

All Science Journal Classification (ASJC) codes

  • Astronomy and Astrophysics
  • Space and Planetary Science

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