054066& 0.000033& a&  hemtemp0& 11.3& d\_1& 152& \\
        MMT\_1348  & 23:33:16.47& +21:29:37.0& 17.59& 17.21& 19.23& 0.37& 4&  0.038449& 0.000025&  &  hemtemp0& 15.6& e\_2& 107& \\
        MMT\_1194  & 23:33:16.56& +21:07:34.0& 20.20& 19.46& 21.58& 0.60& 4&  0.100518& 0.000096&  &    sptemp& 10.5& f\_1& 081& \\
        MMT\_0462  & 23:33:17.47& +21:22:12.6& 19.84& 18.96& 21.36& 0.88& 4&  0.057187& 0.000083&  &m31\_k\_temp& 10.3& f\_1& 026& \\
        MMT\_2464  & 23:33:17.48& +20:50:08.8& 18.83& 17.76& 20.41& 1.06& 4&  0.133259& 0.000077&  &    eltemp& 17.5& d\_1& 154& \\
        MMT\_1199  & 23:33:17.58& +21:09:45.3& 19.78& 19.00& 21.70& 0.64& 4&  0.019790& 0.000081&  &    sptemp& 10.5& f\_1& 015& \\
        MMT\_0451  & 23:33:17.58& +21:23:29.8& 18.13& 17.19& 19.84& 0.94& 4&  0.057222& 0.000051&  &m31\_k\_temp& 18.0& e\_2& 095& \\
        MMT\_2322  & 23:33:17.79& +21:03:31.9& 19.11& 17.96& 20.44& 1.14& 4&  0.132217& 0.000081&  &    eltemp& 17.5& d\_1& 271& \\
        MMT\_1981  & 23:33:17.82& +20:55:55.9& 19.66& 18.95& 21.71& 0.66& 4&  0.248011& 0.000057&  &    sptemp& 20.8& d\_1& 166& \\
        MMT\_0461  & 23:33:18.24& +21:16:19.8& 20.42& 19.32& 21.70& 1.10& 4&  0.165881& 0.000093&  &    sptemp& 13.4& f\_1& 091& \\
        MMT\_0463  & 23:33:18.74& +21:22:39.6& 21.54& 19.84& 22.75& 1.72& 4&  0.290004& 0.000146&  &    eltemp&  9.1& f\_1& 028& \\
        \hline
        \end{tabular}
        \raggedright
        \tablecomments{Magnitudes are from SDSS and are in AB units. An `a' in the alt column indicates the pipeline template choice was overridden. Only a portion of this table is shown here to demonstrate its form and content. A machine-readable version of the full table is available.}
        \end{table*}

        \subsubsection{Redshift measurements}
        MMT spectra were  reduced with the IDL Hectospec
        pipeline {\sc hsred} 2.1, originally written by R.~Cool (\url{http://mmto.org/~rcool/data_tools.html}).  The pipeline, a re-implementation of the one described by \citet{Mink2007}, combined the separate spectra while rejecting cosmic rays, subtracted the sky, and corrected the wavelengths to barycentric values.  The pipeline then cross-correlated each target spectrum with eight spectral templates representing a variety of galaxy spectra.  The template with the highest correlation coefficient was chosen as the initial redshift guess, and the location and width of the correlation peak gave the redshift and its statistical 1$\sigma$ uncertainty.
        There is an additional systematic uncertainty because the chosen template may not best represent the true best fit to the galaxy spectrum.  Table~\ref{t:templates} lists the galaxy templates, the number of times the pipeline chose each one, and the additional uncertainty due to the template choice.
        These uncertainties should be added in quadrature to the individual redshift uncertainties in Table~\ref{t:mmtdata}.

        All spectra were examined by eye and the correlations re-run with {\sc xcsao}, the original cross-correlation routine.  Redshifts from {\sc hsred} and  {\sc xcsao} were consistent within their uncertainties.  For about 10\% of targets, a template other than the initial guess looked to be a better representation of the spectrum, and the initial guess was replaced with the {\sc hsred} redshift for the better template.
        In most cases, the replacement template was chosen for better agreement with emission line velocities than the initial one.  For $\sim$10 targets, none of the {\sc hsred} redshifts matched the spectrum, and an {\sc xcsao} fit was used.  Most of these were spectra with large noise spikes that confused the pipeline but could be deleted manually.

        The visual examination gave each fit a quality ranking $Q$ to code whether the template had correctly identified the spectral features.  $Q=4$ designates an unambiguous redshift based on multiple features of high $S/N$\null.
        $Q=3$ designates a reliable redshift, but the number of features and their $S/N$ is insufficient for $Q=4$\null.  $Q=2$ designates a probable redshift but one with a reasonable chance of features being misidentified.  $Q=1$ designates some indication of a redshift, often a single, weak emission line or multiple features that could be absorption or could be noise.
        $Q=0$ indicates no spectral information, usually very low $S/N$.  Only $Q\ge3$ redshifts are used in this work, though others are included in Table~\ref{t:mmtdata} for completeness.

        \subsubsection{Data quality and success rate}
            \label{sec:mmtsucessrate}

            The success rate is given as a function of the magnitude by
            \begin{equation}\label{eqn:success}
                S(m) = \frac{N_z}{N_\mathrm{targ}} (m)
                \quad,
            \end{equation}
            where $N_z$ is the number galaxies of magnitude $m$ for which a redshift could be measured, and $N_\mathrm{targ}$ is the number of galaxies that were targeted and a spectrum  obtained.
        %
            \figref{fig:mmt_success} shows the success rate as a function of the fiber magnitude.

            \begin{figure}
                \centering
                \includegraphics[width=\linewidth]{A2626_successrate}
                \caption{Fraction of targeted galaxies from which a redshift could be measured. The orange (blue) show the galaxies observed with \numunit{t_\mathrm{int} = 45}{\text{min}} (\numunit{t_\mathrm{int} = 105}{\text{min}}). The full target list is represented by the open black circles. The abscissa scale is SDSS $g$ magnitude in a 2\arcsec\ diameter (``fiber2Mag\_g").}
                \label{fig:mmt_success}
            \end{figure}





        \subsection{Spectroscopic Completeness}
            \label{sec:spec_completeness}
        \begin{figure}
        \centering
        \includegraphics[width=\linewidth,trim=0 18 0 0]
        {A2626_completeness_oneD_lit}
        \caption{(a) Spectroscopic completeness as a function of SDSS $r$ across the A2626 field. Black filled circles show the completeness for the MMT target field with all available redshifts, gray filled circles show it for the entire \numunit{2\times 2}{\deg^2} MeerKAT\xspace \hbox{\ion{H}{1}}\xspace footprint, and black open circles show the completeness for the MMT target field prior to this study. The blue and green dotted vertical lines indicate magnitudes for 70\% and 50\% completeness  for the MMT field. The red dashed line indicates the limiting magnitude for the MMT target catalog before the faint targets were added. (b) Spectroscopic completeness in annuli as a function of distance from the A2626 center. The black filled circles represent the completeness using all available redshifts for galaxies brighter than the $50