A Molecular Filament Threaded by Helical Magnetic Fields?

International audience; We present a multitransition study in the 13CO(1-0), 12CO(2-1),12CO(3-2) and 12CO(4-3) lines of a parsec scale elongated structure connected to a low-mass dense core. Densities larger than n H 2= 104 cm-3 are inferred in the central regions of this structure, supporting the proposition that it is a genuine filament denser than its environment. The sharp observed drop of the 12CO and 13CO emissions requires a power law density fall-off steeper than r -1 although a single density law cannot reproduce the spatial shift of 0.1 pc between the 13CO and 12CO drops. Our results support the previous proposition that this elongated structure is a filament threaded by helical magnetic fields, channeling the gas inflow onto the dense core.