Spectral properties of the BCG. The points denote the flux density of the bright radio core as measured by EMU (dark blue circle) and ATCA (light blue diamonds), while the yellow squares mark the Herschel-SPIRE upper limits on the source flux. The dotted and dashed lines correspond to the power-law spectrum inferred from the EMU and the ATCA data, respectively. The solid line is the modified power law derived by fitting the ALMA and ACA observations jointly with the ATCA flux measurements, with respective 68% credible intervals denoted by the shaded region (Sect. 3.2.3). The mint green vertical bands indicate the frequency ranges covered and the sensitivities achieved by the ALMA (solid) and ACA (hatched) Band 3 and Band 4 observations. Here, the bottom edges of all four bands denote the sensitivity of the corresponding measurements. The radio spectrum of the BCG is measured to become shallower when going to higher frequencies. In yellow is the tentative spectrum for the BCG obtained when including a thermal dust spectral component (Sect. 3.2.2) in addition to a power law model.