High-mass starless clumps from ATLASGAL & SEDIGISM

Here, we use ^13^CO(2-1) line data from the SEDIGISM survey, which covers 78{deg} in longitude (-60{deg}<l<18{deg}, |b|<0.5{deg}) with 30" resolution, to investigate the global dynamical state of these parsec-scale HMSCs (207 sources with good-quality data, mass 10^2^-10^5^M_{sun}_, size 0.1-3.6pc).

We find that most HMSCs are highly turbulent with a median Mach number M_S_~8.2, and 44%-55% of them are gravitationally bound (with virial parameter {alpha}_vir_<~2) if no magnetic fields are present. A median magnetic field strength of 0.33-0.37mG would be needed to support these bound clumps against collapse, in agreement with previous observations of magnetic fields in regions of massive star formation. Luminosity-to-mass ratio, an important tracer of evolutionary stage, is strongly correlated with dust temperature.