We present an extensive spectroscopic follow-up campaign of 29 strong lensing ( SL ) selected galaxy clusters discovered primarily in the Second Red-Sequence Cluster Survey ( RCS-2 ) .
Our spectroscopic analysis yields redshifts for 52 gravitational arcs present in the core of our galaxy clusters , which correspond to 35 distinct background sources that are clearly distorted by the gravitational potential of these clusters .
These lensed galaxies span a wide redshift range of 0.8 \leq z \leq 2.9 , with a median redshift of z _ { s } = 1.8 \pm 0.1 .
We also measure reliable redshifts for 1004 cluster members , allowing us to obtain robust velocity dispersion measurements for 23 of these clusters , which we then use to determine their dynamical masses by using a simulation-based \sigma _ { DM } - M _ { 200 } scaling relation .
The redshift and mass ranges covered by our SL sample are 0.22 \leq z \leq 1.01 and 5 \times 10 ^ { 13 } \leq M _ { 200 } / h ^ { -1 } _ { 70 } M _ { \odot } \leq 1.9 \times 10 ^ { 15 } , respectively .
We analyze and quantify some possible effects that might bias our mass estimates , such as the presence of substructure , the region where cluster members are selected for spectroscopic follow-up , the final number of confirmed members , and line-of-sight effects .
We find that 10 clusters of our sample with N _ { \textnormal { mem } } \gtrsim 20 show signs of dynamical substructure .
However , the velocity data of only one system is inconsistent with a uni-modal distribution .
We therefore assume that the substructures are only marginal and not of comparable size to the clusters themselves .
Consequently , our velocity dispersion and mass estimates can be used as priors for SL mass reconstruction studies and also represent an important step toward a better understanding of the properties of the SL galaxy cluster population .