Probability distribution p(ψ) for ﹩m_{\mathrm{pix}\,}=10^{13}﹩ M_⊙ and ﹩\zeta =40﹩. Dotted, short‐dashed, long‐dashed, and solid curves are for ﹩z=20﹩, 16, 14, and 13, respectively. The top panel shows the PDF of eq. (32), while the bottom panel approximately includes overlap with large bubbles (see text). The filled squares indicate the total probability of the pixel being fully ionized. In the top panel, the upper and lower squares are ﹩z=13﹩ and ﹩z=14﹩, respectively; in the lower panel, only ﹩z=13﹩ has a nonnegligible probability.