A New Approach to Convective Core Overshooting: Probabilistic Constraints from Color-Magnitude Diagrams of LMC Clusters

Abstract

We present a framework to simultaneously constrain the values and uncertainties of the strength of convective core overshooting, metallicity, extinction, distance, and age in stellar populations. We then apply the framework to archival Hubble Space Telescope observations of six stellar clusters in the Large Magellanic Cloud that have reported ages between ~1-2.5 Gyr. Assuming a canonical value of the strength of core convective overshooting, we recover the well-known age-metallicity correlation, and additional correlations between metallicity and extinction and metallicity and distance. If we allow the strength of core overshooting to vary, we find that for intermediate-aged stellar clusters, the measured values of distance and extinction are negligibly effected by uncertainties of core overshooting strength. However, cluster age and metallicity may have disconcertingly large systematic shifts when core overshooting strength is allowed to vary by more than +/- 0.05 Hp. Using the six stellar clusters, we combine their posterior distribution functions to obtain the most probable core overshooting value, 0.500 +0.016 -0.134 Hp, which is in line with canonical values.

37 pages, 13 figures, accepted for publication in the Astrophysical Journal. For data and code to reproduce the figures see, https://philrosenfield.github.io/core_overshoot_clusters . For the stellar evolution models used to in this paper see, https://doi.org/10.5281/zenodo.570192

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