The Near-Infrared Outflow and Cavity of the proto-Brown Dwarf Candidate ISO-Oph 200

TL;DR

This study presents near-infrared observations of a proto-brown dwarf candidate, revealing outflows, cavities, and physical properties that resemble those of protostellar jets, providing insights into brown dwarf formation.

Contribution

First detailed near-infrared integral field study of a proto-brown dwarf, demonstrating outflow and cavity features similar to protostars, and measuring key physical parameters.

Findings

Detected a blue-shifted outflow in H2 and [Fe II] lines.

Estimated outflow mass rates and physical conditions.

Found properties analogous to low-mass protostellar jets.

Abstract

In this letter a near-infrared integral field study of a proto-brown dwarf candidate is presented. A $\sim$ 0\farcs5 blue-shifted outflow is detected in both H$_{2}$ and [Fe II] lines at V$_{sys}$ = (-35~$\pm$ 2)~km~s$^{-1}$ and V$_{sys}$ = (-51~$\pm$ 5)~km~s$^{-1}$ respectively. In addition, slower ($\sim$ $\pm$~10~km~s$^{-1}$) H$_{2}$ emission is detected out to $<$ 5\farcs4, 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 H$_{2}$ emission is tracing a cavity. The source extinction is estimated at A$_{v}$ = 18 mag $\pm$ 1 mag and the outflow extinction at Av = 9 mag $\pm$ 0.4 mag. The H$_{2}$ outflow temperature is calculated to be 1422 K $\pm$~255~K and the electron density of the [Fe II] outflow is measured at $\sim$ 10000 cm$^{-3}$. Furthermore, the mass outflow rate is estimated at $\dot{M}_{out[H2]}$ = 3.8 $\times$ 10$^{-10}$~\Msun~yr$^{-1}$ and $\dot{M}_{out[FeII]}$ = 1 $\times$ 10$^{-8}$~\Msun~yr$^{-1}$. $\dot{M}_{out[FeII]}$ takes a Fe depletion of $\sim$ 88$\%$ into account. The depletion is investigated using the ratio of the [FeII]~1.257~$\mu$m and [PII]~1.188~$\mu$m lines. Using the Pa$\beta$ and Br$\gamma$ lines and a range in stellar mass and radius $\dot{M}_{acc}$ is calculated to be (3 - 10) $\times$ 10$^{-8}$~\Msun~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.