Hot methanol from the inner region of the HH212 protostellar system

The mechanisms leading to the formation of disks around young stellar objects (YSOs) and to the launching of the associated jets are crucial to the understanding of the earliest stages of star and planet formation. HH212 is a privileged laboratory to study a pristine jet-disk system. Therefore we investigate the innermost region (<100AU) around the HH212-MM1 protostar through ALMA band 7 observations of methanol. The 8 GHz bandwidth spectrum towards the peak of the continuum emission of the HH212 system reveals at least 19 transitions of methanol. Several of these lines (among which several vibrationally excited lines in the v(t) = 1, 2 states) have upper energies above 500 K. They originate from a compact (<135AU in diameter), hot (similar to 295 K) region elongated along the direction of the SiO jet. We performed a fit in the uv plane of various velocity channels of the strongest high-excitation lines. The blue-and red-shifted velocity centroids are shifted roughly symmetrically on either side of the jet axis, indicating that the line-of-sight velocity beyond 0.7 km s(-1) from systemic is dominated by rotational motions. The velocity increases moving away from the protostar further indicating that the emission of methanol is not associated with a Keplerian disk or rotating-infalling cavity, and it is more likely associated with outflowing gas. We speculate that CH3OH traces a disk wind gas accelerated at the base. The launching region would be at a radius of a few astronomical units from the YSO.