Upper panel: CMD of K_s vs J − K_s, with the selection box indicated, defined through colour cuts to exclude foreground stars and ensure completeness greater than 80%. The line within the box represents the separation derived by fitting a line to stars exhibiting 50% membership for each of the RC features (see Sect. 3). Lower panel: CMD, with each star colour-coded according to completeness values provided in Surot et al. (2019).