Revealing the structure of the lensed quasar Q 0957+561: III. SMBH mass via gravitational redshift

Abstract

We intend to use the impact of microlensing on the Fe III emission line blend along with a measure of its gravitational redshift to estimate the mass of the quasar's central supermassive black hole (SMBH). We fit the Fe III feature in multiple spectroscopic observations between 2008 and 2016 of the gravitationally lensed quasar Q 0957+561 with relatively high signal-to-noise ratios (at the adequate wavelength). Based on the statistics of microlensing magnifications, we used a Bayesian method to derive the size of its emitting region. The Fe III spectral feature appears systematically redshifted in all epochs of observation by a value of 17 angstroms on average. We find clear differences in the shape of the Fe III line blend between images A and B. Measuring the strength of those magnitude differences, we conclude that this blend may arise from a region of half-light radius of 15 lt-days, which is in good agreement with the accretion disk dimensions for this system. We obtain a mass for the central SMBH of (1.5 +/- 0.5) x 10^9 solar masses, consistent within uncertainties with previous mass estimates based on the virial theorem. The relatively small uncertainties in the mass determination (< 35%) make this method a compelling alternative to other existing techniques (e.g., the virial plus reverberation mapping based size) for measuring black hole masses. Combining the Fe III redshift-based method with the virial, we estimate a virial factor in the 1.2 to 1.7 range for this system.

References in corpus (8)

• The Sloan Digital Sky Survey Reverberation Mapping Project: Estimating Masses of Black Holes in Quasars with Single-Epoch Spectroscopy
• Active galactic nuclei at z ~ 1.5: I. Spectral energy distribution and accretion discs
• Calibration of the virial factor $f$ in supermassive black hole masses of reverberation-mapped AGNs
• New two-colour light curves of Q0957+561: time delays and the origin of intrinsic variations
• Microlensing of the broad emission lines in 27 gravitationally lensed quasars. Broad line region structure and kinematics
• An extended size-luminosity relation for the reverberation-mapped AGNs: the role of the accretion rate
• Near infrared and optical continuum emission region size measurements in the gravitationally lensed quasars Q0957+561 and SBS0909+532
• Revealing the structure of the lensed quasar Q 0957+561: I. Accretion disk size

Cited by in corpus (2)

• Continuum reverberation mapping of the quasar PG 2130+099
• Revealing the structure of the lensed quasar Q 0957+561 III. Constraints on the size of the broad-line region