Near-Infrared Imaging Polarimetry Toward Serpens South: Revealing the Importance of the Magnetic Field

TL;DR

This study uses near-infrared polarization observations to reveal a well-ordered magnetic field in the Serpens South filamentary cloud, showing its role in filament formation and contraction during early cluster development.

Contribution

It provides the first detailed polarization mapping of Serpens South, demonstrating the magnetic field's morphology and strength in relation to filamentary cloud dynamics.

Findings

Magnetic field is perpendicular to the main filament.

Sub-filaments align with the magnetic field.

Magnetic field strength is estimated to be a few hundred microgauss.

Abstract

The Serpens South embedded cluster, which is located at the constricted part in a long filamentary infrared dark cloud, is believed to be in very early stage of cluster formation. We present results of near-infrared (JHKs) polarization observations toward the filamentary cloud. Our polarization measurements of near-infrared point sources indicate a well-ordered global magnetic field that is perpendicular to the main filament, implying that the magnetic field is likely to have controlled the formation of the main filament. On the other hand, the sub-filaments, which converge on the central part of the cluster, tend to run along the magnetic field. The global magnetic field appears to be curved in the southern part of the main filament. Such morphology is consistent with the idea that the global magnetic field is distorted by gravitational contraction along the main filament toward the northern part that contains larger mass. Applying the Chandrasekhar-Fermi method, the magnetic field strength is roughly estimated to be a few x 100 microgauss, suggesting that the filamentary cloud is close to magnetically critical as a whole.