Complex structure of a proto-brown dwarf

Abstract

We present ALMA 12 CO (2-1), 13 CO (2-1), C 18 O (2-1) molecular line observations of a very young proto-brown dwarf system, ISO-OPH 200. We have conducted physical+chemical modelling of the complex internal structure for this system using the core collapse simulations for brown dwarf formation. The model at an age of ∼6000 yr can provide a good fit to the observed kinematics, spectra, and reproduce the complex structures seen in the moment maps. Results from modelling indicate that 12 CO emission is tracing an extended (∼1000 au) molecular outflow and a bright shock knot, 13 CO is tracing the outer (∼1000 au) envelope/pseudo-disc, and C 18 O is tracing the inner (∼500 au) pseudo-disc. The source size of ∼8.6 au measured in the 873𝜇m image is comparable to the inner Keplerian disc size predicted by the model. A 3D model structure of ISO-OPH 200 suggests that this system is viewed partially through a wide outflow cavity resulting in a direct view of the outflow and a partial view of the envelope/pseudo-disc. We have argued that ISO-OPH 200 has been mis-classified as a Class Flat object due to the unusual orientation. The various signatures of this system, notably, the young ∼616 yr outflow dynamical age and high outflow rate (∼1×10 −7 M yr −1 ), silicate absorption in the 10𝜇m mid-infrared spectrum, pristine ISM-like dust in the envelope/disc, comparable sizes of the extended envelope and outflow, indicate that ISO-OPH 200 is an early Class 0 stage system formed in a star-like mechanism via gravitational collapse of a very low-mass core.