a, A three-colour image combining HST V-band/ACS F606W (blue), I-band/ACS F814W (green) and IR-band/WFC3 F125W+F140W+F160W (red) images. This image is the highest-spatial-resolution (full-width at half-maximum ≈ 1.7–2.2 kpc) view of R5519. The numbers under each object denote the ZFOURGE catalogue ID. The contrast of the image is tuned to highlight the double nuclei and tail-like structure of the companion galaxy G5593. b, Blue/Green/Red (HST F125W/F160W/Magellan Kstot) colour image. The Kstot image is a super-deep K-band detection image in ZFOURGE (Methods). This image highlights the resolved ring structure on top of the longest-wavelength image from the ground-based ZFOURGE Kstot band (rest-frame R). The ZFOURGE zp values are labelled in white, with confirmed zs values in yellow. c, Blue/Green/Red (combined rest-frame far UV(FUV)/near UV (NUV)/optical) colour image. The images are generated by stacking HST andZFOURGE catalogue images that correspond to rest-frame FUV, NUV and optical wavelengths (see Supplementary Information). The pixel scale for image a is 0.06″ as sourced from the 3D-HST survey. A pixel scale of 0.15″ is used in b and c to match the ground-based images22. A logarithmic stretch is used for all images in this work.