The near-infrared outflow and cavity of the proto-brown dwarf candidate ISO-Oph 200★

E-ISSN： 1432-0746|610|issue|L19-L19

ISSN： 0004-6361

Source： Astronomy & Astrophysics, Vol.610, Iss.issue, 2018-03, pp. : L19-L19

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Abstract

In this Letter a near-infrared integral field study of a proto-brown dwarf candidate is presented. A ~0.′′5 blue-shifted outflow is detected in both H₂ and [Fe II] lines at V_sys = (–35 ± 2) km s⁻¹ and V_sys = (–51 ± 5) km s⁻¹ respectively. In addition, slower (~±10 km s⁻¹) H₂ emission is detected out to <5.′′4, in the direction of both the blue and red-shifted outflow lobes but along a different position angle to the more compact faster emission. It is argued that the more compact emission is a jet and the extended H₂ emission is tracing a cavity. The source extinction is estimated at A_v = 18 ± 1 mag and the outflow extinction at A_v = 9 ± 0.4 mag. The H₂ outflow temperature is calculated to be 1422 ± 255 K and the electron density of the [Fe II] outflow is measured at ~10 000 cm⁻³. Furthermore, the mass outflow rate is estimated at Ṁ_{out [H₂]} = 3.8 × 10⁻¹⁰ M_⊙ yr⁻¹ and Ṁ_{out[Fe II]} = 1 × 10⁻⁸ M_⊙ yr⁻¹. Ṁ_{out[Fe II]} takes a Fe depletion of ~88% into account. The depletion is investigated using the ratio of the [Fe II] 1.257 μm and [P II] 1.188 μm lines. Using the Paβ and Brγ lines and a range in stellar mass and radius Ṁ_acc is calculated to be (3–10) × 10⁻⁸ M_⊙ yr⁻¹. Comparing these rates puts the jet efficiency in line with predictions of magneto-centrifugal models of jet launching in low mass protostars. This is a further case of a brown dwarf outflow exhibiting analogous properties to protostellar jets.