The Magnetic Field at the Onset of High-mass Star Formation

ABSTRACT :
As part of the MagMaR (Magnetic Fields in Massive Star-forming Regions) survey we have observed in polarization, at ~1000 au resolution, a high-mass core previously believed to be in the prestellar phase. The recently discovered outflow has a dynamical time scale of a few thousand au, indicating that in spite of having a protostar embedded, the core is still very young. This offers the rare opportunity to study the magnetic field in a high-mass core at the onset of star formation. Using the DCF method, we estimate a magnetic field of 3 mG that could not prevent the collapse of the core. The energy balance shows that gravity overwhelms all other energies in place (turbulence and magnetic field). In addition, using observations at ~160 au we show that this core is forming a binary system. We discuss the implications of the magnetic field in the formation of this young binary.