2018ApJ...867....8P

We report for the first time on the magnitude of the intrinsic [Fe/H] spread among 10 old globular clusters (GCs) of the Large Magellanic Cloud (LMC). Such spreads are merely observed in approximately 5% of the Milky Way GCs and recently gained more attention in theoretical models of GC evolution. We derived metallicities with a typical precision of 0.05 dex <= σ[Fe/H] <= 0.20 dex for an average of 14 red giant branch stars per GC from Stromgren photometry. The respective, metallicity-sensitive indices have been calibrated to precise and accurate high-dispersion spectroscopy. For all clusters, we found null [Fe/H] spreads with a typical uncertainty of 0.04 dex, with the possible exception of NGC 1786 that shows an intrinsic dispersion of 0.07 ± 0.04 dex. The mean, observed standard deviation of the derived metallicities for nearly 40% of our GC sample amounted to smaller than 0.05 dex. At present, we cannot exclude the fact that the remaining GCs also have intrinsic Fe-abundance variations in excess of 0.05 dex, but in order to significantly detect those, the measurement errors on individual [Fe/H]-values would need to be lowered to the 0.03-0.07 dex level. These findings suggest, along with those from ages and light element abundances, that the LMC GCs studied here are similar to the majority of Galactic GCs.