A rotating helical filament in the L1251 dark cloud

TL;DR

This study maps a filament in the L1251 dark cloud, revealing its structure, magnetic properties, and evidence of dynamo mechanisms influencing its magnetic field helicities.

Contribution

It provides detailed physical and magnetic characterization of the L1251 filament using NH3 observations, highlighting magnetic helicities and dynamo activity.

Findings

The filament consists of three condensations with opposite magnetic helicities.

Magnetic Reynolds number exceeds 600, indicating significant dynamo action.

The filament's structure spans 38 arcmin by 3 arcmin with elongated morphology.

Abstract

(Abridged) Aims. We derive the physical properties of a filament discovered in the dark cometary-shaped cloud L1251. Methods. Mapping observations in the NH3(1,1) and (2,2) inversion lines, encompassing 300 positions toward L1251, were performed with the Effelsberg 100-m telescope at a spatial resolution of 40 arcsec and a spectral resolution of 0.045 km/s. Results. The filament L1251A consists of three condensations (alpha, beta, and gamma) of elongated morphology, which are combined in a long and narrow structure covering a 38 arcmin by 3 arcmin angular range. The opposite chirality (dextral and sinistral) of the alpha+beta and gamma condensations indicates magnetic field helicities of two types, negative and positive, which were most probably caused by dynamo mechanisms. We estimated the magnetic Reynolds number Rm > 600 and the Rossby number R < 1, which means that dynamo action is important.