Iron yields. The measurements for MKW3s, A2589, and Hydra A, which include only statistical uncertainties, are shown in black. Vertical grey bands around these measurements indicate the systematic uncertainties, accounting for both iron and stellar mass estimates. Observational measurements from Renzini & Andreon (2014) and Ghizzardi et al. (2021b) are shown as the blue boxes and orange triangles, respectively. Golden and brown regions show theoretical models based on supernovae (Renzini & Andreon 2014; Freundlich & Maoz 2021), while the light blue area is the parameterisation by Molendi et al. (2024).