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

Abstract

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"x70" images of Barnard 1b in the 13CO 1->0, C18O 1->0, NH2D 1_{1,1}a->1_{0,1}s, and SO 3_2->2_1 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 ~500au. 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.

arXiv comment9 pages, 4 figures

References in corpus (15)

• Ambipolar diffusion in low-mass star formation. I. General comparison with the ideal MHD case
• Magnetically self-regulated formation of early protoplanetary discs
• Herschel observations of B1-bS and B1-bN: two first hydrostatic core candidates in the Perseus star-forming cloud
• Nitrogen isotopic ratios in Barnard 1: a consistent study of the N2H+, NH3, CN, HCN and HNC isotopologues
• Formation of simple organic molecules in inner T Tauri disks
• Ionization fraction and the enhanced sulfur chemistry in Barnard 1
• Nascent bipolar outflows associated with the first hydrostatic core candidates Barnard 1b-N and 1b-S
• Nitrogen Isotopic Fractionation in Interstellar Ammonia
• Chemical and physical characterization of collapsing low-mass prestellar dense cores
• High spatial resolution imaging of SO and H2CO in AB Auriga: the first SO image in a transitional disk
• Evidence for disks at an early stage in class 0 protostars?
• Reduction of chemical networks. I. The case of molecular clouds
• Molecular content of the circumstellar disk in AB Aur: First detection of SO in a circumstellar disk
• Probing the Earliest Stage of Protostellar Evolution -- Barnard 1-bN and Barnard 1-bS
• Chemical composition of the circumstellar disk around AB Aurigae

Cited by in corpus (8)

• Astrochemical evolution along star formation: Overview of the IRAM Large Program ASAI
• ALMA observations of the young protostellar system Barnard 1b: signatures of an incipient hot corino in B1b-S
• Impact of the Hall effect in star formation and the issue of angular momentum conservation
• Gas-phase Elemental abundances in Molecular cloudS (GEMS) III. Unlocking the CS chemistry: the CS+O reaction
• ALMA observations of envelopes around first hydrostatic core candidates
• Synthetic molecular line observations of the first hydrostatic core from chemical calculations
• PRODIGE VI -- Envelope to Disk with NOEMA: VI. The Missing Sulfur Problem
• Modeling Two First Hydrostatic Core Candidates Barnard 1b-N and 1b-S