Invited Presentation

The magnetic field of the youngest solar-type protostars

Author(s): Maud Galametz (CEA Saclay)

Presenter: Maud Galametz (CEA Saclay, Astrophysics Department)

Magnetic fields are believed to redistribute angular momentum efficiently during the collapse of a protostellar envelope. The position angle of the linearly polarized submm dust emission is often used to probe this magnetic field and tackle its exact role in the star formation processes. As part of the Magnetic YSOs project, we are studying the structure of B in Class 0 protostars. The Class 0 phase is the main accretion phase during which most of the final stellar material is being collected into the protostellar embryo: the role of the magnetic fields during that key stage is unclear and might very well have a key impact on the later evolution of the young star and its surrounding protoplanetary disk before it reaches the main sequence. To study B in the envelopes of Class 0 objects, we have acquired polarization observations of low-mass protostellar cores with the SubMm Array. Our sample contains 12 Class 0 protostars and includes single objects as well as close and wide multiples. Polarization is surprisingly detected in all objects, with polarization degrees ranging from 1-10%. I will discuss how the polarization fraction varies from one of object to the other and how the magnetic field lines align or not with the object outflow. We find for the first time that a relation might exist between the orientation of the magnetic field, the rotational energy at the envelope scale and the presence of fragmentation in the envelopes. We will finally present newly acquired SMA polarization data obtained to complement this analysis.