The Sloan Digital Sky Survey Reverberation Mapping Project: Initial CIV
  Lag Results from Four Years of Data
  We present reverberation-mapping lags and black-hole mass measurements using
the CIV 1549 broad emission line from a sample of 349 quasars monitored as a
part of the Sloan Digital Sky Survey Reverberation Mapping Project. Our data
span four years of spectroscopic and photometric monitoring for a total
baseline of 1300 days. We report significant time delays between the continuum
and the CIV 1549 emission line in 52 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 CIV radius-luminosity
relationship. Our results significantly increase the sample of quasars with CIV
RM results, with the quasars spanning two orders of magnitude in luminosity
toward the high-luminosity end of the CIV radius-luminosity relation. In
addition, these quasars are located at among the highest redshifts (z~1.4-2.8)
of quasars with black hole masses measured with reverberation mapping. This
work constitutes the first large sample of CIV reverberation-mapping
measurements in more than a dozen quasars, demonstrating the utility of
multi-object reverberation mapping campaigns.
