The Sloan Digital Sky Survey Reverberation Mapping Project: Initial C iv Lag Results from Four Years of Data
We present reverberation mapping (RM) lags and black hole mass measurements using the C iv l1549 broad emission line from a sample of 348 quasars monitored as a part of the Sloan Digital Sky Survey RM Project. Our data span four years of spectroscopic and photometric monitoring for a total baseline of 1300 days, allowing us to measure lags up to ~750 days in the observed frame (this corresponds to a rest frame lag of ~300 days in a quasar at z 1.5 and ~190 days at z 3) We report significant time delays between the continuum and the C iv l1549 emission line in 48 quasars, with an estimated false positive detection rate of 10% Our analysis of marginal lag measurements indicates that there are on the order of ~100 additional lags that should be recoverable by adding more years of data from the program. We use our measurements to calculate black hole masses and fit an updated C iv radius luminosity relationship. Our results significantly increase the sample of quasars with C iv RM results, with the quasars spanning two orders of magnitude in luminosity toward the high luminosity end of the C iv radius luminosity relation. In addition, these quasars are located at some of the highest redshifts (z 1.4 2.8) of quasars with black hole masses measured with RM. This work constitutes the first large sample of C iv RM measurements in more than a dozen quasars, demonstrating the utility of multiobject RM campaigns.