Oral Presentation
Extremely Young Protostellar Jets in Orion revealed with ALMA
Presenter: Satoko Takahashi (NAOJ)
We present ~0''.2 (~80 au) resolution observations of the CO (2-1) and SiO (5-4) made with the Atacama millimeter/submillimeter array (ALMA) toward two extremely young intermediate-mass protostellar source, MMS 1 and MMS 6, located in the Orion Molecular Cloud 3 region (OMC-3). We first detected the molecular outflow and jet associated with MMS 1, which is a millimeter source without a bright infrared source wavelength shorter than 70 um. Our result shows clear evidence that MMS 1 already hosts a protostar. For both MMS 1 and MMS 6, we successfully resolved the compact bipolar jets, showing one-side lobe length of ~1000 au, in the SiO (5-4) emission. The detected jets have a very collimated structure (width of ~200 au) with the projected velocity up to ~50-60 km/s. The jets also show a wiggled structure, suggesting a precessing motion. The position-velocity (PV) diagrams of the jets obtained in SiO clearly showed the Hubble-like velocity structure, which show the gas velocity becomes linearly large with respect to the distance from the protostar. We confirmed that the SiO blue-shifted jet in MMS 1 contains three spatially resolved bullets. These bullets show different slopes in the PV diagram. The gas velocity is larger for the inner bullet than the outer ones. The same tendency of gas velocity structure was also found in the SiO blue-shifted jet in MMS 6. The several bullets along the jet implies the episodic mass explosion, which presumably related to the episodic mass accretion process. We also confirmed the deceleration of a bullet located at the tip of the jet, which can be explained by the interaction between the jet and the surrounding material.
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