The chemical evolution of the LMC from APOGEE abundances: a hybrid two-infall OMEGA+ analysis
Year: 2026
Type: preprint
Abstract: The Large Magellanic Cloud (LMC) provides resolved stellar abundances and star-formation histories that can be used together to test models of dwarf-galaxy chemical evolution. We investigated if the non-monotonic APOGEE $[\mathrm{Mg}/\mathrm{Fe}]$-$[\mathrm{Fe}/\mathrm{H}]$ sequence can be explained by a hybrid history that combines a second gas-infall episode with a temporary increase in star-formation efficiency (SFE). We selected 4933 LMC red-giant-branch stars from APOGEE-2 DR17. We fitted an adaptively binned median Mg sequence with the two-zone open-box code OMEGA+. The formal fitting objective contained only the Mg sequence. The metallicity distribution function (MDF), one-dimensional abundance distributions, star-formation history (SFH), present-day mass partition, SFR, and supernova (SN) rate were retained as posterior diagnostics. The best-fitting model reproduces the Mg sequence with an RMS residual of 0.01 dex and also gives a close posterior match to O. It contains two delayed-tau infall episodes, with the second beginning at $t_2=10.39$ Gyr and with integrated mass ratio $M_2/M_1=0.159$, followed by a temporary Gaussian SFE enhancement centred at $t=11.91$ Gyr. The second infall is represented by a mixture of enriched and primordial gas. The model reproduces the timing of the late SFH enhancement and yields a present SFR within the adopted comparison range. A hybrid second-infall and SFE-enhancement history is a plausible scenario for reproducing the observed LMC Mg median sequence. Our fit explains the LMC evolution fairly well, but the remaining small MDF, mass, and SN-rate discrepancies suggest that a selection-function-aware treatment of the stellar distributions is required for a stricter comparison.
Source: arXiv (Cornell University)
Institution: Eötvös Loránd University
Language: English
Subfield: Astronomy and Astrophysics
Field: Physics and Astronomy
Domain: Physical Sciences
Open Access status: green
Funders: Smithsonian Institution, U.S. Department of Energy, Alfred P. Sloan Foundation, Yale University, Carnegie Institution of Washington, Vanderbilt University, Ohio State University, University of Washington, Johns Hopkins University, Carnegie Mellon University, University of Notre Dame, University of Portsmouth, New Mexico State University, York University, University of Oxford, Ministério da Ciência, Tecnologia e Inovação, Universidad Nacional Autónoma de México, Max-Planck-Institut für Astrophysik, Max-Planck-Institut für Astronomie, Instituto de Astrofísica de Canarias, Office of Science, University of Colorado Boulder, Leibniz-Gemeinschaft, Lawrence Berkeley National Laboratory
OpenAlex ID: W7223098677