the uncertainty in the ionizing emissivity to just that in the escape fraction, $f_{\rm esc}$. In other words, the total ionizing luminosity, $L_{\rm ion}$ is roughly proportional to the product of the non-ionzing UV luminosity ($L_{\rm UV}$) and $f_{\rm esc}$: $L_{\rm ion}(M) \propto f_{\rm esc}(M)L_{\rm UV}(M)$. Our fiducial choice of a constant $\zeta$ implies $L_{\rm ion}\propto M$, from which we can obtain an expression for $L_{\rm UV}(M)$ using our power-law expression for $M(M_{\rm UV})$ to recover $L_{\rm UV}(M)\propto M^{0.68}$ for the faint end of the luminosity function. Therefore, our illustrative, single population model at $z=8$ roughly translates to $f_{\rm esc}\propto M^{0.32}$.

### How does the 21 cm PS depend on the [EoR]{} parameters? {#sec:variation}

In Fig. \[fig:3param\_variation\], we highlight how each individual [EoR]{} parameter affects the 21 cm PS, and also provide a visual representation of the total noise profiles for each telescope. In all panels, we show the mock $z=9$ observation for our fiducial [EoR]{} parameters (solid black curve) which results in $\bar{x}_{{\ifmmode\mathrm{H\,{\scriptscriptstyle I}}\else{}H\,{\scriptsize I}\fi}{}} = 0.71$. In order to facilitate the discussion, we decompose the 21 cm PS to first order (neglecting the contribution from redshift-space distortions and spin temperature fluctuations), $$\begin{aligned}
 \label{eq:decomp}
\Delta^{2}_{21}(k) &\propto& \bar{x}^{2}_{{\ifmmode\mathrm{H\,{\scriptscriptstyle I}}\else{}H\,{\scriptsize I}\fi}{}}\Delta^{2}_{\delta\delta}(k) 