The Outflow from the Luminous Young Stellar Object IRAS 20126+4104: From 4000 AU to 0.4 pc

Abstract

We have imaged the outflow from the luminous young stellar object IRAS 20126+4104 (I20126) with the Submillimeter Array in CO (3-2), HCN (4-3), and SiO (5-4) at 1''-2'' resolutions within a radius of ~20'' from the central driving source. Our observations reveal at least three different components of the outflowing gas: (1) A compact (~4000 AU) bipolar outflow toward the central young stellar object. With a dynamical timescale of ~120 yr, this component represents a very new jet/outflow activity in I20126. (2) A collimated outflow with an extent of ~0.2 pc previously detected in SiO (2-1). Both morphology and kinematics favor this component being a jet-driven bow shock system. (3) An S-shaped CO outflow with an extent of ~0.4 pc. This component records the precession history very well. Its kinematic feature, where the velocity increases with distance from the YSO, indicates, independently of other evidence, that the outflow axis is moving toward the plane of the sky. The three outflow components record the history of the primary jet precession over scales ranging from a few hundred AU to approximately 0.4 pc. Our results indicate that CO (3-2) emission is a good tracer to probe the primary jet. The gas densities and SiO relative abundances in I20126 shocks are estimated using the large velocity gradient calculations. The inferred SiO abundances of (1-5) × 10-8 in I20126 outflow lobes are comparable to the expected enhancement at shocked regions.