Gemini/GMOS Spectroscopy of 26 Strong Lensing Selected Galaxy Cluster
  Cores
  We present results from a spectroscopic program targeting 26 strong lensing
cluster cores that were visually identified in the Sloan Digital Sky Survey
(SDSS) and the Second Red-Sequence Cluster Survey (RCS-2). The 26 galaxy
cluster lenses span a redshift range of 0.2 < z < 0.65, and our spectroscopy
reveals 69 unique background sources with redshifts as high as z=5.200. We also
identify redshifts for 262 cluster member galaxies and measure the velocity
dispersions and dynamical masses for 18 clusters where we have redshifts for N
\geq 10 cluster member galaxies. We include an accounting for the expected
biases in dynamical masses of strong lensing selected clusters as predicted by
results from numerical simulations and discuss possible sources of bias in our
observations. The median dynamical mass of the 18 clusters with N \geq 10
spectroscopic cluster members is M_{Vir} = 7.84 x 10^14 M_sun h_{0.7}^{-1},
which is somewhat higher than predictions for strong lensing selected clusters
in simulations. The disagreement is not significant considering the large
uncertainty in our dynamical data, systematic uncertainties in the velocity
dispersion calibration, and limitations of the theoretical modeling.
Nevertheless our study represents an important first step toward characterizing
large samples of clusters that are identified in a systematic way as systems
exhibiting dramatic strong lensing features.
