A SPECTROSCOPIC SURVEY of the FIELDS of 28 STRONG GRAVITATIONAL LENSES

We present the spectroscopic redshift catalog from a wide-field survey of the fields of 28 galaxy-mass strong gravitational lenses. We discuss the acquisition and reduction of the survey data, collected over 40 nights of 6.5 m MMT and Magellan time, employing four different multiobject spectrographs. We determine that no biases are introduced by combining data sets obtained with different telescope and spectrograph combinations. Special care is taken to determine redshift uncertainties using repeat observations. The redshift catalog consists of 9,768 new and unique galaxy redshifts. 82.4% of the catalog redshifts are between z = 0.1 and z = 0.7, and the catalog median redshift. The data from this survey will be used to study the lens environments and line-of-sight structures to gain a better understanding of the effects of large-scale structure on lens statistics and lens-derived parameters.