Dynamical modeling of the C iv broad line region of the z=2.805 multiply imaged quasar SDSS J2222+2745

Peter R. Williams, Tommaso Treu, Håkon Dahle, Stefano Valenti, Louis Abramson, Aaron J. Barth, Brendon J. Brewer, Karianne Dyrland, Michael Gladders, Keith Horne, Keren Sharon

Research output: Contribution to journalArticlepeer-review


We present the first ever models of a broad line region (BLR) at the peak of active galactic nucleus (AGN) activity using the multiply imaged z = 2.805 quasar SDSS J2222+2745. The modeled data consist of monthly spectra covering the broad C IV emission line over a 5.3 yr baseline. The models suggest a thick disk BLR that is inclined by degrees 40 degrees to the observer's line of sight and with an emissivity weighted median radius of = rmedian = 33.0(-2.1)(+2.44) light days. The kinematics are dominated by near-circular Keplerian motion with the remainder inflowing. The restframe lag one would measure from the models is taumedian = 36.4(-1.8)(+1.8) days, which is consistent with measurements based on cross-correlation. We show a possible geometry and transfer function based on the model fits and find that the model-produced velocity-resolved lags are consistent with those from cross-correlation. We measure a black hole mass of log10(MBH/M⊙) = 8.31(-0.06)(+0.07), which requires a scale factor of log10 (fmean,σ) = 0.20(-0.07)(+0.09.). This is the most precise MBH measurement for any AGN at cosmological distances and it demonstrates that the precision required for BH-host coevolution studies is attainable.
Original languageEnglish
Number of pages6
JournalAstrophysical Journal Letters
Issue number1
Publication statusPublished - 30 Jun 2021


  • Strong gravitional lensing
  • Active galactic nuclei
  • Supermassive black holes
  • Quasars
  • Astronomy data modelling


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