Stromlo Stellar Tracks: non-solar scaled abundances for massive stars

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K. Grasha, L.J. Kewley, A. Roy, R.S. Sutherland

We present the Stromlo Stellar Tracks, a set of stellar evolutionary tracks, computed by modifying the Modules for Experiments in Stellar Astrophysics (MESA) 1D stellar evolution package, to fit the Galactic Concordance abundances for hot (T>8000 K) massive (≥10M⊙) Main-Sequence (MS) stars. Until now, all stellar evolution tracks are computed at solar, scaled-solar, or alpha-element enhanced abundances, and none of these models correctly represent the Galactic Concordance abundances at different metallicities. This paper is the first implementation of Galactic Concordance abundances to the stellar evolution models. The Stromlo tracks cover massive stars (10≤M/M⊙≤300) with varying rotations (v/vcrit=0.0,0.2,0.4) and a finely sampled grid of metallicities (−2.0≤[Z/H]≤+0.5; Δ[Z/H]=0.1) evolved from the pre-main sequence to the end of 12Carbon burning. We find that the implementation of Galactic Concordance abundances is critical for the evolution of main-sequence, massive hot stars in order to estimate accurate stellar outputs (L, Teff, g), which, in turn, have a significant impact on determining the ionizing photon luminosity budgets. We additionally support prior findings of the importance that rotation plays on the evolution of massive stars and their ionizing budget. The evolutionary tracks for our Galactic Concordance abundance scaling provide a more empirically motivated approach than simple uniform abundance scaling with metallicity for the analysis of \HII\ regions and have considerable implications in determining nebular emission lines and metallicity. Therefore, it is important to refine the existing stellar evolutionary models for comprehensive high-redshift extragalactic studies. The Stromlo tracks are publicly available to the astronomical community online.

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