Infrared luminosity (top left) and SFR (derived from the emission at FUV and 24 μm, bottom left) versus . The upper limit of IZw18 is shown as a red star, in comparison with the galaxies described in Sect. 4. In the two panels on the left, the blue dashed lines show the correlation by Gao & Solomon (2004) and the red dashed lines show the linear fit of the metal-poor galaxies (Shi et al. 2015, 2016; Hunt et al. 2015; Cormier et al. 2014, DGS). The bottom right panel shows the empirically derived broken power-law regression for /SFR as a function of metallicity, illustrating the decrease of α_CO with metallicity as introduced by Hunt et al. (2020). The error bar of IZw18 represents the uncertainty in the measurements of the stellar mass. We note that in the panels, all the circles represent the global properties of the galaxies, while the magenta crosses denote the star-forming regions.