Structured velocity field in the inner envelope of B335: ALMA observations of rare CO isotopologues

Abstract

Studying Class 0 objects is very important, as it allows to characterize dynamical processes at the onset of the star formation process, and to determine the physical mechanisms responsible for the outcome of the collapse. Observations of dense gas tracers allow the characterization of key kinematics of the gas directly involved in the star-formation process, such as infall, outflow or rotation. This work aims at investigating the molecular line velocity profiles of the Class 0 protostellar object B335 and attempts to put constraints on the infall motions happening in the circumstellar gas of the object.} Observations of C${}^{17}$O (1-0), C${}^{18}$O (1-0) and ${}^{12}CO$ (2-1) transitions are presented and the spectral profiles are analyzed at envelope radii between 100 and 860 au. C${}^{17}$O emission presents a double peaked line profile distributed in a complex velocity field. Both peaks present an offset of 0.2 to 1 km s${}^{-1}$ from the systemic velocity of the source in the probed area. The optical depth of the C${}^{17}$O emission has been estimated and found to be less than 1, suggesting that the two velocity peaks trace two distinct velocity components of the gas in the inner envelope. After discarding possible motions that could produce the complex velocity pattern, such as rotation and outflow, it is concluded that infall is producing the velocity field. Because inside-out symmetric collapse cannot explain those observed profiles, it is suggested that those are produced by non-isotropic accretion from the envelope into the central source along the outflow cavity walls.

13 pages, 8 figures. To be published in A&A

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Cited by in corpus (5)

• PRODIGE -- Envelope to Disk with NOEMA II. Small-scale temperature structure and a streamer feeding the SVS13A protobinary using CH3CN and DCN
• Magnetically regulated collapse in the B335 protostar? II. Observational constraints on gas ionization and magnetic field coupling
• Models of Rotating Infall for the B335 Protostar
• Increasing mass-to-flux ratio from the dense core to the protostellar envelope around the Class 0 protostar HH 211
• Physical conditions for dust grain alignment in Class 0 protostellar cores I. Observations of dust polarization and molecular irradiation tracers