摘要：Aims. We determine the proper motion of protostellar jets around Class 0 and Class I sources in an active star forming region in Serpens.
Methods. Multi-epoch deep images in the 2.122 μm line of molecular hydrogen, v = 1−0 S(1), obtained with the near-infrared instrument NOTCam on a timescale of 10 years, are used to determine the proper motion of knots and jets. K-band spectroscopy of the brighter knots is used to supply radial velocities, estimate extinction, excitation temperature, and H2 column densities towards these knots.
Results. We measure the proper motion of 31 knots on different timescales (2, 4, 6, 8, and 10 years). The typical tangential velocity is around 50 km s-1 for the 10-year baseline, but for shorter timescales, a maximum tangential velocity up to 300 km s-1 is found for a few knots. Based on morphology, velocity information, and the locations of known protostars, we argue for the existence of at least three partly overlapping and deeply embedded flows, one Class 0 flow and two Class I flows. The multi-epoch proper motion results indicate time-variable velocities of the knots, for the first time directly measured for a Class 0 jet. We find in general higher velocities for the Class 0 jet than for the two Class I jets. While the bolometric luminosites of the three driving sources are about equal, the derived mass flow rate Ṁout is two orders of magnitude higher in the Class 0 flow than in the two Class I flows.
关键词：stars: formation;ISM: jets and outflows;Herbig-Haro objects;ISM: kinematics and dynamics
