AFGL 5180 ALMA, LUCI and HST images

Bright jet knots outflowing from the central most massive protostar, S4 (estimated mass ~11M_{sun}_, via SED fitting), are detected towards the east of the source and are resolved in fine detail with the AO imaging. Additional knots are distributed throughout the field, likely indicating the presence of multiple driving sources. Sub-millimeter sources detected by ALMA are shown to be grouped in two main complexes, AFGL 5180 M and a small cluster ~15" (0.15pc in projection) to the south, AFGL 5180 S. From our NIR continuum images we identify YSO candidates down to masses of ~0.1M_{sun}_.

Combined with the sub-mm sources, this yields a surface number density of such YSOs of N*~10^3pc^-2^ within a projected radius of about 0.1pc. Such a value is similar to those predicted by models of both Core Accretion from a turbulent clump environment and Competitive Accretion. The radial profile of N* is relatively flat on scales out to 0.2pc, with only modest enhancement around the massive protostar inside 0.05pc, which provides additional constraints on these massive star formation models.

This study demonstrates the utility of high-resolution NIR imaging, in particular with AO, for detecting outflow activity and YSOs in distant regions. The presented images reveal the complex morphology of outflow-shocked gas within the large-scale bipolar flow of a massive protostar, as well as clear evidence for several other outflow driving sources in the region. Finally, this work presents a novel approach to compare the observed YSO surface number density from our study against different models of massive star formation.