Distribution of the rate of merging BBHs formed through CHE per unit chirp mass and unit effective spin that is observable from Earth with a detector with infinite sensitivity, derived from the simulations of dB20. We refer to these rates as “cosmological”. Numbers are normalized to the maximum value of the differential rate dR/dM_chirp/dχ_eff. The two panels highlight predicted systems below and above the PISN gap. The dashed white contour corresponds to the predicted region below the PISN gap that arises from CHE, computed with the semi-analytical model shown in Fig. 5.