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section{Previous measurements}
\citet{JIMMY13} measured the stellar kinematics and photometry of the galaxies in our sample, we summarise their method and results in this section.
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\subsection{Stellar Kinematics}\label{sec:ppxf}
First a signal-to-noise ratio (SNR) cut of 5 across all the spaxels (spatial pixels) was applied. The spaxels were then re-binned to a minimum SNR of 10, using the spatial binning Voronoi code of \citet{CAPPELLARI03}. The velocity and line-of-sight velocity dispersion were computed using the penalised fitting scheme of \citet[pPXF;][]{PPXF}, and the MILES \citep[Medium-resolution Isaac Newton Telescope Library of Empirical Spectra; ][]{MILES} library stellar templates. pPXF fits the stellar library templates to the absorption line features of the BCG spectra, giving the redshifts and the broadening of the spectral lines.
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\textbf{The angular momentum} was characterised by the $\lambda_{\rm R}$ parameter defined by \citet{EMSELLEM07}. It is calculated as follows:
\begin{equation}
\lambda_{\rm R} \sim \frac{\langle R |V| \rangle}{\langle R\sqrt{V^2+\sigma^2 \rangle}},
\end{equation}
where $R$ represents the radius of the galaxy, V is the stellar velocity and $\sigma$ the velocity dispersion. The numerator and denominator are luminosity weighted. A higher $\lambda_{\rm R}$ represents a higher angular momentum. \textbf{The ellipticity ($\epsilon$)} at the effective radius of each galaxy was measured using the publicly available IDL routine $find\_galaxy.pro$ developed
by Michele Cappellari\footnote{http://www-astro.physics.ox.ac.uk/$\sim$mxc/idl/}. Following \citet{EMSELLEM11}, the values of $\lambda_{\rm R}$ and $\epsilon$ can be used to distinguish fast and slow rotators (FR and SR respectively) by using the threshold:
\begin{equation} \label{eq:FR}
\lambda_{\rm R} \geq (0.31 \pm 0.01)\times \sqrt{\epsilon},
\end{equation}
where FRs lie above this threshold and SRs lie below.\\\\
\textbf{The dynamical mass} was measured using the standard equation given in \citet{CAPPELLARI06}.
\begin{equation}\label{eq:mass}
M_{dyn}=\frac{5R_e \sigma_e^2}{G},
\end{equation}
where $\sigma_e$ is the aperture corrected velocity dispersion of the integrated spectrum within the effective radius; G is the gravitational constant. In Table \ref{tab:kin} we summarise the relevant kinematic results. 7 of the BCGs are SR and 2 are FR. For $\sigma_{e}, \epsilon_e$ and $\lambda_{R_e}$ we refer the reader to Table 2 of \citet{JIMMY13}.
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\subsection{Photometric Analysis}
\citet{JIMMY13} analysed the photometry of this sample using images from SDSS Data Release 3. They measured the effective radius by fitting a 2D de Vaucouleurs profile. They also analysed the presence of recent mergers using the Gini, and M$_{\rm 20}$ coefficients \citep{LOTZ08}. This method studies the distribution of light looking for irregularities that could indicate morphological signatures of mergers. A galaxy is a merger candidate if it crosses the threshold:
\begin{equation}\label{eq:merger}
G \geq -0.14M_{20} + 0.33
\end{equation}
Where M$_{\rm 20}$ is the 2nd order moment of the brightest 20~per~cent of pixels, and G is the Gini coefficient. In the case of gas-poor galaxies like our sample, a galaxy will be above the threshold if it is currently merging or has merged in the last 0.2~Gyr \citep{LOTZ11}. 4 of the BCGs in the sample are merging. The relevant kinematic and photometric results of \citet{JIMMY13} are presented in Table \ref{tab:kin}.
