High-mass Starless Clumps: Dynamical State and Correlation between Physical Parameters

Abstract

In order to study the initial conditions of massive star formation, we have previously built a sample of 463 high-mass starless clumps (HMSCs) across the inner Galactic plane covered by multiple continuum surveys. Here, we use 13 CO(2–1) line data from the SEDIGISM survey, which covers 78° in longitude (−60° < l < 18°, ∣ b ∣ < 0.°5) 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 ⊙ , size 0.1–3.6 pc). We find that most HMSCs are highly turbulent with a median Mach number   ∼ 8.2 , and 44%–55% of them are gravitationally bound (with virial parameter α vir ≲ 2) if no magnetic fields are present. A median magnetic field strength of 0.33–0.37 mG 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. Magnetic field strength is also correlated with density. The Larson line width–size scaling does not hold in HMSCs. This study advances our understanding of the global properties of HMSCs, and our high-resolution observations with the Atacama Large Millimeter/submillimeter Array are in progress to study the resolved properties.