Dynamical Modeling of the CIV Broad Line Region of the $z=2.805$ Multiply Imaged Quasar SDSS J2222+2745

TL;DR

This study models the broad line region of a high-redshift quasar using 5.3 years of data, revealing a thick, inclined disk with near-circular Keplerian motion and estimating the black hole mass.

Contribution

First detailed dynamical modeling of the CIV broad line region in a multiply imaged high-redshift quasar, providing insights into its geometry, kinematics, and black hole mass.

Findings

BLR modeled as a thick inclined disk with 40° tilt.

Median radius of the CIV emitting region is ~33 light days.

Black hole mass estimated at approximately 2 billion solar masses.

Abstract

We present CIV BLR modeling results for the multiply imaged $z=2.805$ quasar SDSS J2222+2745. Using data covering a 5.3 year baseline after accounting for gravitational time delays, we find models that can reproduce the observed emission-line spectra and integrated CIV fluctuations. The models suggest a thick disk BLR that is inclined by $\sim$40 degrees to the observer's line of sight and with a emissivity weighted median radius of $r_{\rm median} = 33.0^{+2.4}_{-2.1}$ light days. The kinematics are dominated by near-circular Keplerian motion with the remainder inflowing. The rest-frame lag one would measure from the models is $\tau_{\rm median} = 36.4^{+1.8}_{-1.8}$ 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 $\log_{10}(M_{\rm BH}/M_\odot) = 8.31^{+0.07}_{-0.06}$, which requires a scale factor of $\log_{10}(f_{{\rm mean},\sigma}) = 0.20^{+0.09}_{-0.07}$.