The dominance of turbulence over magnetism in the formation of massive star cluster seeds
摘要
High-mass stars form in protoclusters, where gravo-magnetic processes elongate collapsing clouds and clumps preferentially perpendicular to magnetic (B) fields. Yet it remains unclear whether gravo-magnetic processes still govern the formation of 0.01-pc-scale condensations in massive star-forming protoclusters, which are crucial for understanding the stellar initial mass function and multiplicity. Here we report on statistical evidence that the condensation elongations are preferentially aligned with local B fields, based on dust polarization observations towards 30 massive star-forming regions with the Atacama Large Millimeter/submillimeter Array. Our clustered massive star formation simulations reveal that this more parallel alignment is exclusively observed in models where the initial turbulence dominates the B fields. By contrast, models in which the initial B fields dominate the turbulence distinctly exhibit a more perpendicular alignment. The comparison between observations and simulations indicates that turbulence could play a more important role than B fields in the formation of condensations in the context of clustered massive star formation. Moreover, we find a possibly turbulence-induced preferential misalignment between the B field and rotation axis of condensations, which may potentially reduce the magnetic braking efficiency and facilitate massive disk formation. Our findings indicate that turbulence could be more critical than previously thought in determining the initial stellar properties.