Chemical segregation in the young protostars Barnard 1b-N and S
1 Observatorio Astronómico Nacional (OAN, IGN), Apdo 112, 28803 Alcalá de Henares, Spain
2 LERMA, Observatoire de Paris, PSL Research University, CNRS, Sorbonne Universités, UPMC Univ. Paris 06, École Normale Supérieure, 75005 Paris, France
3 Institut de Radioastronomie Millimétrique (IRAM), 300 rue de la Piscine, 38406 Saint Martin d’ Hères, France
4 Centre de Recherche Astronomique de Lyon (CRAL), École Normale Supérieure de Lyon, CNRS-UMR 5574, 69364 Lyon Cedex 07, France
5 Instituto de Ciencia de Materiales de Madrid (ICMM-CSIC). 28049 Cantoblanco, Madrid, Spain
6 National Radio Astronomy Observatory, 520 Edgemont Road, Charlottesville, VA 22903, USA
Received: 10 April 2017
Accepted: 18 August 2017
The extremely young Class 0 object B1b-S and the first hydrostatic core (FSHC) candidate, B1b-N, provide a unique opportunity to study the chemical changes produced in the elusive transition from the prestellar core to the protostellar phase. We present 40″ × 70″ images of Barnard 1b in the 13CO 1 → 0, C18O 1 → 0, NH2D 11,1a→ 10,1s, and SO 32→ 21 lines obtained with the NOEMA interferometer. The observed chemical segregation allows us to unveil the physical structure of this young protostellar system down to scales of ~500 au. The two protostellar objects are embedded in an elongated condensation, with a velocity gradient of ~0.2–0.4 m s-1 au-1 in the east-west direction, reminiscent of an axial collapse. The NH2D data reveal cold and dense pseudo-disks (R ~ 500 − 1000 au) around each protostar. Moreover, we observe evidence of pseudo-disk rotation around B1b-S. We do not see any signature of the bipolar outflows associated with B1b-N and B1b-S, which were previously detected in H2CO and CH3OH, in any of the imaged species. The non-detection of SO constrains the SO/CH3OH abundance ratio in the high-velocity gas.
Key words: astrochemistry / ISM: clouds / ISM: individual objects: Barnard 1b / stars: formation / stars: low-mass / ISM: kinematics and dynamics
Based on observations carried out with the IRAM Northern Extended Millimeter Array (NOEMA). IRAM is supported by INSU/ CNRS (France), MPG (Germany), and IGN (Spain).
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© ESO, 2017