Kinematics

Medium-resolution spectroscopic observations combined with AO of the inner regions of the DG Tau, RW Aur, HL Tauzcma, and SVS 13 microjets have been obtained with the integral field spectrograph OASIS(CFHT) in the optical domain [19, 28, 29] and/or in the near-infrared with the IRCS(SUBARU) [37, 38] and NACO(VLT) [11] instruments in the long-slit mode. HST/STIS long-slit observations have been also published on the DG Tau, RW Aur, TH 28 and LkHa321 microjets by [5, 6, 9, 45, 46].

Channel maps reconstructed from the IFS OASIS/CFHT observations (Fig. 5) clearly show an onion-like kinematical structure for the flow, with high velocity material more concentrated towards the jet axis than low velocity material [29]. This effect has been also detected in higher angular resolution HST observations [5]. Detailed kinematics along the jet axis have been investigated so far for 3 microjets: DG Tau, RW Aur and HL Tau. Figure 6 (right panel) shows a position-velocity diagram along the RW Aur jet axis in the near-infrared [Fe ii] 1.644 |m emission line obtained by [38] with the IRCS/SUBARU spectrograph and AO correction (velocity resolution 30 kms-1, angular resolution 0."15-0."2). These observations illustrate the fact that the acceleration scale of the HVC flow is below current resolution (< 30 AU). Terminal centroid flow velocities range from 150 to 350 kms-1. Moderate variations along the jet axis of 10-20% of the average flow velocity are observed for the HVC on scales less than 3" from the source.

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