Top to bottom: Various quantities in orbital-plane slices from the ‘radiative’ simulation: density (ρ), local diffusion time (t_diff, Eq. (11)), kinetic plus potential energy per unit mass (e_kp), opacity (κ), and the density-weighted hydrogen ionisation fraction ([HII]). Left to right: Snapshots representative of the pre-plunge-in phase, the end of the rapid plunge-in, and the late-time slow spiral-in. In rows (d) and (e), we overlay contours where the optical depth equals 1, 3, and 10, from largest to smallest size. The contours in row (d) include the contribution from all material, whereas those in row (e) include only the contribution from bound material (e_kp>0). The fact that these contours enclose the hydrogen partial ionisation zone (marked by the sharp transition between green and pink) suggests that a significant fraction of hydrogen recombination energy could be absorbed by the bound material.