3D magnetic-field morphology of the Perseus molecular cloud

Abstract : Context. Despite recent observational and theoretical advances in mapping the magnetic fields associated with molecular clouds, their three-dimensional (3D) morphology remains unresolved. Multi-wavelength and multi-scale observations will allow us to paint a comprehensive picture of the magnetic fields of these star-forming regions.
Aims: We reconstructed the 3D magnetic field morphology associated with the Perseus molecular cloud and compared it with predictions of cloud-formation models. These cloud-formation models predict a bending of magnetic fields associated with filamentary molecular clouds. We compared the orientation and direction of this field bending with our 3D magnetic-field view of the Perseus cloud.
Methods: We used previous line-of-sight and plane-of-sky magnetic field observations as well as Galactic magnetic field models to reconstruct the complete 3D magnetic field vectors and morphology associated with the Perseus cloud.
Results: We approximated the 3D magnetic field morphology of the cloud as a concave arc that points in the decreasing longitude direction in the plane of the sky (from our point of view). This field morphology preserves a memory of the Galactic magnetic field. In order to compare this morphology to cloud-formation model predictions, we assume that the cloud retains a memory of its most recent interaction. After incorporating velocity observations, we find that the line-of-sight magnetic field observations are consistent with predictions of shock-cloud-interaction models.
Conclusions: To our knowledge, this is the first time that the 3D magnetic fields of a molecular cloud have been reconstructed. We find the 3D magnetic field morphology of the Perseus cloud to be consistent with the predictions of the shock-cloud-interaction model that describes the formation mechanism of filamentary molecular clouds.