We present high resolution (0.2", 1000 AU) 1.3 mm ALMA observations of massive infrared dark cloud clump, G028.37+00.07-C1, thought to harbor the early stages of massive star formation. Using N2D+(3-2) we resolve the previously identified C1-S core, separating the bulk of its emission from two nearby protostellar sources. C1-S is thus identified as a massive (∼50M⊙), compact (∼0.1pc diameter) starless core, e.g., with no signs of outflow activity. Being highly deuterated, this is a promising candidate for a pre-stellar core on the verge of collapse. An analysis of its dynamical state indicates a sub-virial velocity dispersion compared to a trans-Alfv\'enic turbulent core model. However, virial equilibrium could be achieved with sub-Alfv\'enic conditions involving ∼2mG magnetic field strengths.
@article{arxiv.1701.05953,
title = {Zooming in to Massive Star Birth},
author = {Shuo Kong and Jonathan C. Tan and Paola Caselli and Francesco Fontani and Ke Wang and Michael J. Butler},
journal= {arXiv preprint arXiv:1701.05953},
year = {2018}
}