Mass accretion and ejection are the fundamental processes during the early stages of star formation. We have conducted the first extensive study of the accretion and outflow properties in Class 0/I proto-brown dwarfs (proto-BDs) using VLT SINFONI spectroscopy and spectro-imaging observations. The near-infrared spectra for the proto-BDs show prominent emission in the Paschen β, Brackett γ, Brackett 10–19, and several [FeII] and H2 lines. The detection of H2 lines from vibrational energy levels of ν = 1 to ν = 6 indicates the presence of both a cold (E(v,J) < 6000 K) and a hot gas component (E(v,J) > 20,000 K). The Class 0 proto-BDs show strong emission in the H2 lines but the [Fe II] lines are undetected, while the Class I objects show emission in both [Fe II] and H2 lines, suggesting an evolutionary trend in the jets from a molecular to an ionic composition. Extended emission with knots is seen in the [Fe II] and H2 spectro-images for 3 proto-BDs, while the rest show compact morphologies with a peak on-source. The peak velocities of the [Fe II] lines (≥100 km/s) are higher than the H2 lines (∼10-50 km/s), indicating that these lines trace different flow components. The accretion and outflow activity rates for the proto-BDs are in the range of (2×10−6 - 5×10−9) M⊙/yr. The outflow rate derived using the [Fe II] lines is at least an order of magnitude higher than H2 lines, indicating that [Fe II] traces a large fraction of the total outflow mass. A comparison with Class 0/I protostars indicates that there is no notable decline in the accretion and outflow activity or jet efficiencies over a wide range in bolometric luminosities from ~30 L⊙ down to ~0.03 L⊙.

{"references": ["Riaz & Bally, 2021, MNRAS, 501, 3781"]}