(a) Average IMF-weighted stellar yield of He from massive stars as a function of the initial stellar metallicity, as predicted by the stellar models of Nomoto et al. (2013, black solid line) and Limongi & Chieffi (2018) for different stellar rotational velocities; in particular, the blue, green, and orange lines correspond to the Limongi & Chieffi (2018) stellar models with v_rot = 0, 150, and 300 km s⁻¹, respectively. (b) Average IMF-weighted stellar yield of He from AGB stars as a function of initial stellar metallicity, as predicted by the stellar models of Karakas (2010, black solid line) and Ventura et al. (2013, blue solid line).