ArXiv · 2026
We examine the galactic chemical evolution (GCE) of ³rmHe in one-zone and multi-zone models, with particular attention to the stellar yields and GCE parameters that can reproduce both the protosolar ³rmHe abundance and recent gas-phase ³rmHe/⁴rmHe measurements in the Orion nebula. Published stellar models indicate negligible net ³rmHe production by massive stars, while the predicted yields from asymptotic giant branch (AGB) stars are metallicity-dependent and span a range of ∼ 2.5 depending on the extra mixing processes incorporated in the stellar models. The dominant contribution to ³rmHe production comes from 1-2 M_⊙ stars, making ³rmHe evolution slow compared to other AGB elements and to Fe enrichment from Type Ia supernovae. We constrain our GCE models to reproduce the observed [O/H] in the interstellar medium, and our fiducial models adopt an empirically motivated IMF-averaged oxygen yield y_(rm O) ≈ 1.2 Z_(rm O, ⊙). Even with the lowest of the AGB ³rmHe yields, based on stellar models with rotational and thermohaline mixing, our GCE models tend to overpredict the protosolar and Orion ³rmHe abundances; they require a slow onset of star formation and low star formation efficiency to come close to the observed values. With a higher oxygen yield, calibration to observed [O/H] implies stronger outflows, making it easier to reproduce the observed ³rmHe. Alternatively, the true ³rmHe yield could be lower than that predicted by existing stellar models, suggesting that mixing in red giants is not yet fully captured. Future ³rmHe measurements that probe higher metallicity environments could help distinguish these possibilities.
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