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CAB Home » Radio astronomy » News » Publications - IRAS 21391+5802: The Molecular Outflow and Its Exciting Source
IRAS 21391+5802: The Molecular Outflow and Its Exciting Source

Beltrán, Maria T.; Girart, José M.; Estalella, Robert; Ho, Paul T. P.; Palau, Aina

We present centimeter and millimeter observations of gas and dust around IRAS 21391+5802, an intermediate-mass source embedded in the core of IC 1396N. Continuum observations from 3.6 cm to 1.2 mm are used to study the embedded objects and overall distribution of the dust, while molecular line observations of CO, CS, and CH3OH are used to probe the structure and chemistry of the outflows in the region. The continuum emission at centimeter and millimeter wavelengths has been resolved into three sources separated ~15" from each other, and with one of them, BIMA 2, associated with IRAS 21391+5802. The dust emission around this source shows a very extended envelope, which accounts for most of the circumstellar mass of 5.1 Msolar. This source is powering a strong molecular outflow, elongated in the east-west direction, which presents a complex structure and kinematics. While at high outflow velocities the outflow is clearly bipolar, at low outflow velocities the blueshifted and redshifted emission are highly overlapping and the strongest emission shows a V-shaped morphology. The outflow as traced by CS and CH3OH exhibits two well-differentiated and clumpy lobes, with two prominent northern blueshifted and redshifted clumps. The curved shape of the clumps and the spectral shape at these positions are consistent with shocked material. In addition, CS and CH3OH are strongly enhanced toward these positions with respect to typical quiescent material abundances in other star-forming regions. This kinematical and chemical evidence suggests that the clumps are tracing gas entrained within the surface of interaction between the molecular outflow and the dense ambient quiescent core and that the morphology of the molecular outflow is a result of this interaction. The circumstellar mass together with the power-law index of the dust emissivity measured, ?=1.1+/-0.3, and the fact that the source is driving a molecular outflow are consistent with the source BIMA 2 being an embedded intermediate-mass protostar. In addition, the source fits very well correlations between source and outflow properties found for low-mass Class 0 objects. The other two sources in the region, BIMA 1 and BIMA 3, have a mass of 0.07 Msolar each, and their dust emissivity index, ?<0.3 and ?=0.1+/-0.3, respectively, is consistent with more evolved objects. BIMA 1 is also driving a very collimated and small bipolar outflow elongated in the north-south direction.

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