A high-resolution imaging survey of massive young stellar objects in the Magellanic Clouds

Kavli Affiliate: Gregory Herczeg

| First 5 Authors: Venu M. Kalari, Ricardo Salinas, Hans Zinnecker, Monica Rubio, Gregory Herczeg

| Summary:

Constraints on the binary fraction of young massive stellar objects (mYSOs)
are important for binary and massive star formation theory. Here, we present
speckle imaging of 34 mYSOs located in the Large (1/2 $Z_{odot}$) and Small
Magellanic Clouds ($sim$1/5 $Z_{odot}$), probing projected separations
between the 2000-20000 au (at angular scales of 0.02-0.2") range, for stars
above 8 $M_{odot}$. 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$pm$5%, and
$<$5%, respectively. We rule out a wide binary fraction greater than 35% in the
Large, 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
$Z_{odot}$), which within the physical parameter space probed by this study is
$sim$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,
statistically more significant samples of high-mass systems in low-metallicity
environments, and for comparison in the Milky Way, are essential to confirm or
repudiate our claim.

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