The Black Hole Mass of the z = 2.805 Multiply Imaged Quasar SDSS J2222+2745 from Velocity-resolved Time Lags of the C iv Emission Line

Abstract

Abstract We present the first results of a 4.5 yr monitoring campaign of the three bright images of multiply imaged z = 2.805 quasar SDSS J2222+2745 using the Gemini North Multi-Object Spectrograph and the Nordic Optical Telescope. We take advantage of gravitational time delays to construct light curves surpassing 6 yr in duration in the observed frame and achieve an average spectroscopic cadence of 10 days during the 8 months of visibility per season. Using multiple secondary calibrators and advanced reduction techniques, we achieve percent-level spectrophotometric precision and carry out an unprecedented reverberation mapping analysis, measuring both integrated and velocity-resolved time lags for the C iv emission line. The full line lags the continuum by τ cen = 36.5 − 3.9 + 2.9 rest-frame days. We combine our measurement with published C iv emission line lags and derive the r BLR − L relationship log 10 ​ ( τ / d a y ) = ( 0.99 ± 0.07 ) + ( 0.48 ± 0.03 ) log 10 ​ [ λ L λ ( 1350 A A ) / 10 44 e r g s − 1 ] with 0.30 ± 0.06 dex intrinsic scatter. The velocity-resolved lags are consistent with circular Keplerian orbits, with τ cen = 86.2 − 5.0 + 4.5 , 25 − 15 + 11 , and 7.5 − 3.5 + 4.2 rest-frame days for the core, blue wing, and red wing, respectively. Using σ line with the mean spectrum and assuming log 10 ( f mean , σ ) = 0.52 ± 0.26 , we derive log 10 ( M BH / M ⊙ ) = 8.63 ± 0.27 . Given the quality of the data, this system represents a unique benchmark for calibration of M BH estimators at high redshift. Future work will present dynamical modeling of the data to constrain the virial factor f and M BH.