Reverberation Mapping of Luminous Quasars at High-z

TL;DR

This study uses reverberation mapping to measure emission line lags in high-redshift quasars, updating radius-luminosity relations and comparing black hole mass estimates from RM and single-epoch methods.

Contribution

It provides the first radius-luminosity relations for Ly_alpha, SiIV, and CIII] lines in high-z quasars and compares RM-based black hole masses with single-epoch estimates.

Findings

Significant emission line lags measured for Ly_alpha, SiIV, CIV, and CIII].

Updated radius-luminosity relations for multiple UV lines at high redshift.

RM-based black hole masses are generally smaller than single-epoch estimates.

Abstract

We present Reverberation Mapping (RM) results for 17 high-redshift, high-luminosity quasars with good quality R-band and emission line light curves. We are able to measure statistically significant lags for Ly_alpha (11 objects), SiIV (5 objects), CIV (11 objects), and CIII] (2 objects). Using our results and previous lag determinations taken from the literature, we present an updated CIV radius--luminosity relation and provide for the first time radius--luminosity relations for Ly_alpha, SiIV and CIII]. While in all cases the slope of the correlations are statistically significant, the zero points are poorly constrained because of the lack of data at the low luminosity end. We find that the emissivity weighted distance from the central source of the Ly_alpha, SiIV and CIII] line emitting regions are all similar, which corresponds to about half that of the H_beta region. We also find that 3/17 of our sources show an unexpected behavior in some emission lines, two in the Ly_alpha light curve and one in the SiIV light curve, in that they do not seem to follow the variability of the UV continuum. Finally, we compute RM black hole masses for those quasars with highly significant lag measurements and compare them with CIV single--epoch (SE) mass determinations. We find that the RM-based black hole mass determinations seem smaller than those found using SE calibrations.