The magnetic structure of Class~0 protostars

The MagneticYSOs project aims at characterizing the role of magnetic fields during the early stages of star formation, when most of the final stellar mass is being built. The position angle of linearly polarized submm dust emission is often used to probe the magnetic field. In order to study the structure of magnetic fields on 750-2000 AU scales, we have acquired interferometric polarization observations of low-mass protostellar cores with the SMA at 345GHz. Our sample contains 9 Class 0 protostars and includes single objects as well as close and wide multiples. Polarization is detected in all objects, with polarization degrees ranging from 1-6%. In this presentation, I will compare the SMA continuum maps with previous observations of these objects and present the distribution of the polarized intensity, fraction, angle. I will quantify how the orientation of the magnetic field lines aligns with the object outflow and how it compares with magn etic field lines derived at other wavelengths. I will finally discuss how the polarization fraction varies with the source intensity and how it relates to the multiplicity of the sources (globules \/ binary) and their envelope mass