Volume 595, November 2016
|Number of page(s)||6|
|Published online||28 October 2016|
Hot methanol from the inner region of the HH 212 protostellar system
1 Max-Planck-Institut für Radioastronomie, Auf dem Hügel 69, 53121 Bonn, Germany
2 INAF, Osservatorio Astrofisico di Arcetri, Largo E. Fermi 5, 50125 Firenze, Italy
3 LERMA, Observatoire de Paris, PSL Research University, CNRS, Sorbonne Universités, UPMC Univ. Paris 06, École Normale Supérieure, 75014 Paris, France
4 IRAM, 300 rue de la Piscine, 38406 Saint-Martin-d’ Hères, France
5 IGN, Observatorio Astronómico Nacional, Alfonso XII 3, 28014 Madrid, Spain
6 Univ. Grenoble Alpes, CNRS, IPAG, 38000 Grenoble, France
7 LERMA, Département de physique de l’ENS, ENS, Observatoire de Paris, PSL Research University, Université Cergy-Pontoise, Université Paris Seine, Sorbonne Universités, UPMC Univ. Paris 06, CNRS, Paris, France
Received: 2 August 2016
Accepted: 12 October 2016
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. HH 212 is a privileged laboratory to study a pristine jet-disk system. Therefore we investigate the innermost region (<100 AU) around the HH 212-MM1 protostar through ALMA band 7 observations of methanol. The 8 GHz bandwidth spectrum towards the peak of the continuum emission of the HH 212 system reveals at least 19 transitions of methanol. Several of these lines (among which several vibrationally excited lines in the νt = 1,2 states) have upper energies above 500 K. They originate from a compact (<135 AU in diameter), hot (~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.
Key words: stars: formation / ISM: jets and outflows / ISM: molecules / ISM: individual objects: HH 212
© ESO, 2016
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