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

Astron Astrophys

National Radio Astronomy Observatory, 520 Edgemont Road, Charlottesville, VA 22903, USA.

Published: October 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 CO 1→0, CO 1→0, NHD 1→1, 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.

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http://www.ncbi.nlm.nih.gov/pmc/articles/PMC5662144PMC
http://dx.doi.org/10.1051/0004-6361/201730963DOI Listing

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