Extended Data Fig. 4: Numerical models of energy injection into an expanding cloud of merger ejecta.
The left panel provides color maps of the density (left) and a tracer of the original electron fraction (Ye, right) in velocity space as resulting after 1 day for four ejecta models in which different amounts of heating energy (0, 5, 10, and 30 MeV per baryon) were injected during roughly the first second of expansion. While the density distribution can be made spherical with large injection energies, the Ye stratification remains nearly unchanged. The right panel shows a model where a relativistic wind with 60° half-opening angle around the polar axis is injected. The plots display the same quantities as in the left panels for four different time steps. The wind inflates the innermost part of the ejecta, creating a hot low-density bubble, and launches a shock wave, which dissipates energy predominantly in the polar ejecta, allowing them to spread sideways and, by that, reduce the pole-to-equator variation of Ye.
