Abstract
We report the detection of a molecular outflow driven by the brown dwarf binary FU Tau. Using the IRAM 30 m telescope we observed the $^{12}$CO(2-1) (CO) emission in the vicinity of FU Tau and detected a bipolar outflow by examining the wings of the CO(2-1) line as we moved away from the source position. An integrated map of the wing emission between 3 kms$^{-1}$ and 5 kms$^{-1}$ reveals a blue-shifted lobe at a position of $\sim$ 20 \arcsec\ from the FU Tau system and at a position angle of $\sim$ 20$^{\circ}$. The beam size of the observations is $11\arcsec$\ hence it is not possible to distinguish between the two components of the FU Tau binary. However as optical forbidden emission, a strong tracer of the shocks caused by outflow activity, has been detected in the spectrum of FU Tau A we assume this component to be the driving source of the molecular outflow. We estimate the mass and mass outflow rate of the outflow at 4 $\times$ 10$^{-6}$ \Msun\ and 6 $\times$ 10$^{-10}$ \Msun/yr respectively. These results agree well with previous estimates for BD molecular outflows. FU Tau A is now the third BD found to be associated with molecular outflow activity and this discovery adds to the already extensive list of the interesting properties of FU Tau.
Highlights
Young brown dwarfs (BDs) occupy the mass regime between stars and planets and are significant in any theory describing activity in star-forming regions
We report the detection of a molecular outflow driven by the brown dwarf binary FU Tau
Since optical forbidden emission, a strong tracer of the shocks caused by outflow activity, has been detected in the spectrum of FU Tau A, we assume that this component is the driving source of the molecular outflow
Summary
Young brown dwarfs (BDs) occupy the mass regime between stars and planets and are significant in any theory describing activity in star-forming regions. We have conducted a survey of young BDs with the IRAM 30 m telescope in the 12CO(1−0) and 12CO(2−1) to test this hypothesis (Whelan et al, in prep.) Their approach is to target BDs known to be accreting and that show evidence of outflow activity primarily in the form of FELs, in a mass range of 0.02 M to 0.13 M , including a few very low-mass stars (VLMSs). Evidence of outflow activity comes from the detection of the [O I]λ 5577 and [O I]λ 6300 forbidden lines in an optical spectrum of FU Tau A (Stelzer et al 2010) All of these facts combined show that the FU Tau system is probably a rarity among BDs, and it is of considerable interest to test models describing the formation and evolution of BDs. All of these facts combined show that the FU Tau system is probably a rarity among BDs, and it is of considerable interest to test models describing the formation and evolution of BDs For this reason we chose to publish the discovery of its molecular outflow separately from the overall presentation of our IRAM survey
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