2013MNRAS.434L..16F

Over the past 20 years reverberation mapping has proved one of the most successful techniques for studying the local (<1 pc) environment of supermassive black holes that drive active galactic nuclei. Key successes of reverberation mapping have been direct black hole mass estimates, the radius-luminosity relation for the Hβ line and the calibration of single-epoch mass estimators commonly employed up to z ∼ 7. However, observing constraints mean that few studies have been successful at z > 0.1, or for the more-luminous quasars that make up the majority of current spectroscopic samples, or for rest-frame ultraviolet emission lines available in optical spectra of z > 0.5 objects. Previously, we described a technique for stacking cross-correlations to obtain reverberation mapping results at high z. Here, we present the first results from a campaign designed for this purpose. We construct stacked cross-correlation functions for the C iv and Mg ii lines and find a clear peak in both. We find that the peak in the Mg ii correlation is at longer lags than C iv consistent with previous results at low redshift. For the C iv sample, we are able to bin by luminosity and find evidence for increasing lags for more-luminous objects. This C iv radius-luminosity relation is consistent with previous studies but with a fraction of the observational cost.