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

TL;DR

This study uses far-infrared polarimetry to reveal a new transition in magnetic field orientation within Serpens South, indicating magnetic supercriticality and the onset of star cluster formation at high densities.

Contribution

It reports the discovery of a novel magnetic field orientation transition at high column densities, advancing understanding of magnetic influence on star formation.

Findings

Magnetic field orientation transitions from perpendicular to parallel at high densities.

Magnetic supercriticality occurs near $A_V\gtrsim 21$ mag, enabling gravitational collapse.

Star cluster formation begins in regions where magnetic support weakens.

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 $A_V\gtrsim{}3~\rm{}mag$. 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 $A_V\gtrsim{}21~\rm{}mag$ in parts of the Serpens South cloud. This transition appears to be caused by gas flow and indicates that magnetic supercriticality sets in near $A_V\gtrsim{}21~\rm{}mag$, allowing gravitational collapse and star cluster formation to occur even in the presence of relatively strong magnetic fields.