Chemical segregation in the young protostars Barnard 1b-N and S: evidence of pseudo-disk rotation in Barnard

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 CO 1 → 0, CO 1 → 0, NHD 1a→ 1s, and SO 3→ 2 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 au in the east-west direction, reminiscent of an axial collapse. The NHD 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 HCO and CHOH, in any of the imaged species. The non-detection of SO constrains the SO/CHOH abundance ratio in the high-velocity gas.We thank the Spanish MINECO for funding support from grants CSD2009-00038, AYA2012-32032, AYA2016-75066-C2-1/2-P, and ERC under ERC-2013-SyG, G. A. 610256 NANOCOSMOS. E.R. and M.G. thank the INSU/CNRS program PCMI for funding

Chemical segregation in the young protostars Barnard 1b-N and S

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