Impact of mass-size slopes, that is density gradients, on CMZ star formation. The gray shading is taken from Fig. 3. The brown-orange shading indicates where spheres would exceed the star formation density threshold. The shading gradient indicates the uncertainty in n_SF,lim, here taken to be in the range 10^{7 to 8} cm^-3. The orange cross and dashed line indicate the mass-size trend observed for G0.253+0.016. The green crosses and dashed line indicate the mass-size relation of a model cloud that has the same total mass and size as G0.253+0.016, but follows a more shallow mass-size relation (i.e., steeper density gradient), which is taken here from observations of Orion. The error bar indicates a representative uncertainty in mass measurements by a factor 2 (Sect. 3). In summary this diagram shows that shallow CMZ density laws help to suppress star formation because little or no gas at all exceeds n_SF,lim.