August 21 Wed 14:30-15:30
ALMA-J Seminar
hybrid; Room 102 in ALMA Building and Zoom
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=============== August 21 Wed===============
Seminar: ALMA-J Seminar
Date and time: August 21st, 2024 (Wed.), 14:30-15:30 JST
Place: ALMA Building Room 102 / Zoom (hybrid)
Speaker: Satoko Takahashi (NAOJ ALMA Project / SOKENDAI)
Title: An extremely Young Protostellar Core, MMS1/OMC-3: Episodic mass ejection history traced by the micro SiO jet.
High-angular resolution and high sensitivity achieved with ALMA enabled us to detect candidates of extremely young protostellar sources, which are not detected even at 70um while exhibit very compact / young molecular jet (~1000 au / ~100 yr). They are considered to be in a phase right after the protostar formation and show the first mass ejection history. In this talk, I present ~0.2 arcsec resolution observations of the CO (2–1) and SiO (5–4) lines made with the ALMA toward an extremely young intermediate-mass protostellar source, MMS 1 located in the Orion Molecular Cloud-3 region. We have successfully imaged a very compact CO molecular outflow (~2000 au) and a collimated SiO jet (< 1000 au). The maximum jet speed is estimated to be as high as 93 km/s. The SiO jet wiggles and displays a chain of knots. These are the first direct evidences that MMS 1 already hosts a protostar. The position-velocity (PV) diagram shows two distinct structures: (i) bow-shocks associated with the tips of the outflow, and (ii) a collimated jet, showing the jet velocities linearly increasing with the distance from the driving source. Comparisons between the observations and numerical simulations quantitatively share similarities such as multiple-mass ejection events within the jet and Hubble-like flow associated with each mass ejection event. Finally, our ALMA jet study was compared with a submillimeter flux variability study performed with JCMT/SCUBA2. While there is a weak flux decline seen in the 850um light curve obtained with JCMT/SCUBA2 toward MMS1, no dramatic flux change events are detected. This suggests that there has not been a clear burst event associated with the mass accretion onto the protostar within the last 8 years.
Organizers : Kshitiz Mallick, Yuichi Matsuda