taken with the auxiliary-port camera (ACAM), with an exposure time of 6000s. Full details of the $i'$ data are available in @Cooke2015. The $J$ band image was obtained with the long-slit intermediate resolution infrared spectrograph (LIRIS), with an exposure time of 8160s, and reduced in the standard way using the publicly available program THELI [@Erben2005; @Schirmer2013]. A $3\sigma$ depth is reached at $i'=26.0$mag and $J=23.6$mag, with seeing of $\sim 0.76$arcsec for both images.

The IRAC images have a much broader point-spread function (PSF) than the $i'$ and $J$ images, so selecting sources using the 4.5image is prone to blending and some galaxies may be missed which are distinct in the $i'$ or $J$ bands. Using solely the $i'$ band to detect sources would result in biasing the selection towards intrinsically blue sources, whereas the $J$ image is relatively shallow, so we use a deep F140W image as a detection image. The field around C was imaged with the F140W filter of the *Hubble Space Telescope* Wide-Field Camera 3 (*HST*/WFC3) in July 2015 as part of an on-going 40-orbit spectroscopic program (P.I. D. Stern). The *HST* spectra and photometry will be discussed in a future paper (Noirot et al., in preparation). 