Magnetized filamentary gas flows feeding the young embedded cluster in Serpens South

Abstract

Observations indicate that molecular clouds are strongly magnetized, and that magnetic fields influence the formation of stars. A key observation supporting the conclusion that molecular clouds are significantly magnetized is that the orientation of their internal structure is closely related to that of the magnetic field. At low column densities the structure aligns parallel with the field, whereas at higher column densities, the gas structure is typically oriented perpendicular to magnetic fields, with a transition at visual extinctions $A_V\gtrsim 3\mathrm{mag}$. Here we use far-infrared polarimetric observations from the HAWC+ polarimeter on SOFIA to report the discovery of a further transition in relative orientation, i.e., a return to parallel alignment at $A_V\gtrsim 21\mathrm{mag}$ in parts of the Serpens South cloud. This transition appears to be caused by gas flow and indicates that magnetic supercriticality sets in near $A_V\gtrsim 21\mathrm{mag}$, allowing gravitational collapse and star cluster formation to occur even in the presence of relatively strong magnetic fields.

16 pages, 4 figures, Published in Nature Astronomy (August 2020). This is the authors' version before final edits. Link to the NA publication: https://www.nature.com/articles/s41550-020-1172-6

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• CARMA Large Area Star Formation Survey: Observational Analysis of Filaments in the Serpens South Molecular Cloud
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• Magnetically Dominated Parallel Interstellar Filaments at the Infrared Dark Cloud G14.225-0.506
• Far-infrared polarimetry from the Stratospheric Observatory for Infrared Astronomy
• Star-forming filament models

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