High-mass stars usually form in giant molecular clouds (GMCs) as part of a young stellar cluster, but some isolated O/B stars are observed. What are the initial conditions that lead to the formation of these objects? The aim of this study is to measure the distribution and basic physical properties of the neutral gas associated with isolated intermediate- and high-mass young stellar objects (YSOs) in the Large Magellanic Cloud.
As part of the SAGE Spitzer Legacy program for the LMC, we have identified and confirmed YSOs using Spitzer IRAC photometry and IRS spectroscopy. By examining the spatial coincidence between the YSOs and 12CO(1–0) emission detected by the NANTEN mapping survey, we identified more than one hundred intermediate/massive YSOs in the LMC that appear to be isolated, i.e. not associated with CO emission. Deeper follow-up CO observations by our team with the higher resolution by Mopra Telescope (beam=30”) detected CO emission at the YSO positions for ~80% of the isolated LMC YSOs. We obtained ALMA data of some of the targets during Cycle 2. We targeted a small but representative (in terms of their association with neutral gas tracers) sample of the isolated high-mass YSOs that we have been studying in the LMC. All of our 12 targets are separated by more than 200 pc from known CO clouds. Our analysis of the ALMA data shows that a compact molecular cloud whose mass is a few thousand solar masses or smaller is associated with most of the YSOs.