Proper Motion of H2O Masers in IRAS 20050+2720 MMS1: An AU Scale Jet Associated with An Intermediate-Mass Class 0 Source

Abstract

We conducted a 4 epoch 3 month VLBA proper motion study of H${}_2$O masers toward an intermediate-mass class 0 source IRAS 20050+2720 MMS1 (d=700 pc). From milli-arcsecond (mas) resolution VLBA images, we found two groups of H2O maser spots at the center of the submillimeter core of MMS1. One group consists of more than $\sim 50$ intense maser spots; the other group consisting of several weaker maser spots is located at 18 AU south-west of the intense group. Distribution of the maser spots in the intense group shows an arc-shaped structure which includes the maser spots that showed a clear velocity gradient. The spatial and velocity structures of the maser spots in the arc-shape did not significantly change through the 4 epochs. Furthermore, we found a relative proper motion between the two groups. Their projected separation increased by 1.13+/-0.11 mas over the 4 epochs along a line connecting them. The spatial and velocity structures of the intense group and the relative proper motions strongly suggest that the maser emission is associated with a protostellar jet. Comparing the observed LSR velocities with calculated radial velocities from a simple biconical jet model, we conclude that the most of the maser emission are likely to be associated with an accelerating biconical jet which has large opening angle. The large opening angle of the jet traced by the masers would support the hypothesis that poor jet collimation is an inherent property of luminous (proto)stars.

arXiv comment14 pages, 10 figures, Fig.3 was downsized significantly. accepted for publication in A&A

References in corpus (3)

• Proper Motion of Water Masers Associated with IRAS 21391+5802: Bipolar Outflow and an AU-Scale Dusty Circumstellar Shell
• Water Masers as Tracers of Protostellar Disks and Outflows in the Intermediate Mass Star Forming Region NGC 2071
• VLA Observations of H2O Masers in the Class 0 Protostar S106 FIR: Evidence for a 10 AU-Scale Accelerating Jet-like Flow

Cited by in corpus (10)

• A Multi-Epoch, Simultaneous Water and Methanol Maser Survey toward Intermediate-Mass Young Stellar Objects
• A high resolution study of complex organic molecules in hot cores
• On the nature of outflows in intermediate-mass protostars: a case study of IRAS 20050+2720
• Time-Resolved AU-Scale Jets Traced by Masers in the IRAS 4A/B Regions of NGC1333
• Submillimeter Array Observations of 321 GHz Water Maser Emission in Cepheus A
• Infall, outflow, and rotation in the G19.61-0.23 hot molecular core
• A collimated jet and an infalling-rotating disk in G192.16-3.84 traced by H2O maser emission
• The extremely collimated bipolar H_2O jet from the NGC 1333-IRAS 4B protostar
• Water and Methanol Maser Survey of Protostars in the Orion Molecular Cloud Complex
• A Proper Motion Study of the Haro 6-10 Outflow: Evidence for a Subarcsecond Binary