SMA observations of the magnetic fields around a low-mass protostellar system.

Observations of the submillimeter polarized dust emission is an important tool to study the role of the magnetic fields in the evolutions of molecular clouds and in the star formation processes. The Submillimeter Array (SMA) is the first imaging submillimeter interferometer. The installation of quarter wave plates in front of the 345 GHz receivers has allowed to carry out polarimetric observations. We present high angular resolution 345 GHz SMA observations of polarized dust emission towards the low-mass protostellar system NGC 1333 IRAS 4A. We show that in this system the observed magnetic field morphology is in agreement with the standard theoretical models of formation of low-mass stars in magnetized molecular clouds at scales of a few hundred AU; gravity has overcome magnetic support and the magnetic field traces a clear hourglass shape. The magnetic field is substantially more important than turbulence in the evolution of the system and the initial misalignment of the magnetic and spin axes may have been important in the formation of the binary system. [ABSTRACT FROM AUTHOR]