Astronomy and Astrophysics, volume 498, 753-759 (2009/5-2)
The extremely collimated bipolar H2O jet from the NGC1333-IRAS4B protostar.
DESMURS J.-F., CODELLA C., SANTIAGO-GARCIA J., TAFALLA M. and BACHILLER R.
Abstract (from CDS):
We have performed observations of water maser emission towards a sample of low-mass protostars, in order to investigate the properties of jets associated with the earliest stages of star formation and their interaction with the surrounding medium. The main aim is to measure the absolute positions and proper motions of the H2O spots in order to investigate the kinematics of the region from where the jet is launched. We imaged the protostars in the nearby region NGC1333-IRAS4 in the water maser line at 22.2GHz by using the VLBA in phase-reference mode at the milliarcsecond scale over four epochs, spaced by one month to measure proper motions. Two protostars (A2 and B) were detected in a highly variable H2O maser emission, with an active phase shorter than four weeks. The H2O maps allow us to trace the fast jet driven by the B protostar: we observed both the red- and blue-shifted lobes very close to the protostar, ≤35AU, moving away with projected velocities of ∼10-50km/s. The comparison with the molecular outflow observed at larger scale suggests a jet precession with a 18'/yr rate. By measuring the positional spread of the H2O spots we estimate a jet width of ∼2AU at a distance of ∼12AU from the driving protostar.
stars: formation - radio lines: ISM - ISM: jets and outflows - ISM: molecules - masers