25 AU Angular Resolution Observations of HH 211 with ALMA : Jet Properties and Shock Structures in SiO, CO, and SO

Abstract

HH 211 is a highly collimated jet with a chain of knots and a wiggle structure on both sides of a young Class 0 protostar. We used two epochs of Atacama Large Millimeter/submillimeter Array (ALMA) data to study its inner jet in the CO(J=3-2), SiO(J=8-7), and SO(N_J=8_9-7_8) lines at $\sim$25 AU resolution. With these ALMA and previous 2008 Submillimeter Array (SMA) data, the proper motion of 8 knots within $\sim$250 AU of the central source is found to be $\sim$0.068" per year ($\sim$102 km/s), consistent with previous measurements in the outer jet. At $\sim$4 times higher resolution, the reflection-symmetric wiggle can be still fitted by a previously proposed orbiting jet source model. Previously detected continuous structures in the inner jet are now resolved, containing at least 5 sub-knots. These sub-knots are interpreted in terms of a variation in the ejection velocity of the jet with a period of $\sim$4.5 years, shorter than that of the outer knots. In addition, backward and forward shocks are resolved in a fully-formed knot, BK3, and signatures of internal working surface and sideways ejection are identified in Position-Velocity diagrams. In this knot, low-density SO and CO layers are surrounded by a high-density SiO layer.

References in corpus (5)

• Shells, jets, and internal working surfaces in the molecular outflow from IRAS 04166+2706
• Submillimeter arcsecond-resolution mapping of the highly collimated protostellar jet HH 211
• Jet Motion, Internal Working Surfaces, and Nested Shells in the Protostellar System HH 212
• Anatomy of the internal bow shocks in the IRAS 04166+2706 protostellar jet
• A Pseudodisk Threaded with a Toroidal and Pinched Poloidal Magnetic Field Morphology in the HH 211 Protostellar System

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• The Effelsberg survey of FU Orionis and EX Lupi objects I. -- Host environments of FUors/EXors traced by NH${}_3$
• Jets in Low-Mass Protostars
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