EW comparison of the MUSE He II λ1640 sample using BPASS stellar population models. Left: C III]λ1907+C III]λ1909 EW vs. He II λ1640 EW. Right: O III]λ1666 EW vs. He II λ1640 EW. Galaxies with S/N ≥ 2.5 are shown by stars, and others are shown as lower limits to the EW as triangles. We compare our observed EWs with model tracks from the Xiao et al. (2018) BPASS binary tracks. Models were computed for a log₁₀(n_H) = 1.0 and U_s = −1.5 at different metallicities between 2 Z_⊙ to 1/200th Z_⊙. The size of the symbols increases with time. EWs from the literature are also shown for comparison.