Ratio between C₂H(1–0) J = 1∕2–1∕2 and HCN(1–0) for EFF1, EFF4 and EFF5. We use this ratio to put an upper limit to x(e⁻) in the gas traced by HCN using the models of Bron et al. (2021) (right axis). Top: ratio between C₂ H(1–0) J = 1∕2–1∕2 F = 0–1 and HCN(1–0) for EFF1, EFF4 and EFF5. Bottom: ratio between C₂H(1–0) J = 1∕2–1∕2 F = 1–1 and HCN(1–0) for EFF1, EFF4 and EFF5. The intensity of the F = 1–1 line is scaled to that of the F = 0–1 line by assuming a 2:1 ratio. The ratios are computed by averaging over a slice of 2′ in the Dec direction centered in the regions. The offsets are shown along the RA direction and are referenced to the center of the region (Table 2). Inverted triangles show 3σ upper limits.