A High-resolution Imaging Survey of Massive Young Stellar Objects in the Magellanic Clouds

Abstract

Constraints on the binary fraction of massive young stellar objects (mYSOs) are important for binary and massive star formation theory. Here, we present speckle imaging of 34 mYSOs located in the Large Magellanic Cloud (1/2 Z ⊙) and Small Magellanic Cloud (∼1/5 Z ⊙), probing projected separations in the 2000 to 20,000 au (at angular scales of 0.″02–0.″2) range, for stars above 8 M ⊙. We find two wide binaries in the Large Magellanic Cloud (from a sample of 23 targets), but none in a sample of 11 in the Small Magellanic Cloud, leading us to adopt a wide binary fraction of 9% ± 5% and <5%, respectively. We rule out a wide binary fraction greater than 35% in the Large Magellanic Cloud and 38% in the Small Magellanic Cloud at the 99% confidence level. This is in contrast to the wide binary fraction of mYSOs in the Milky Way (presumed to be 1 Z ⊙), which within the physical parameter space probed by this study is ∼15%–60% from the literature. We argue that while selection effects could be responsible for the lower binary fraction observed, it is more likely that there are underlying physical mechanisms responsible for the observed properties. This indicates that metallicity and environmental effects may influence the formation of wide binaries among massive stars. Future larger, more statistically significant samples of high-mass systems in low-metallicity environments for comparison to the Milky Way, are essential to confirm or repudiate our claim.