Herbig-Haro jets in 3D: the HL/XZ Tauri region

Abstract

Context. Jets and outflows from young stellar objects (YSOs) can be identified and traced through the distribution and structure of shocked emission-line features. To understand the formation of these regions requires kinematic data at high spectral resolution and with full spatial coverage. Aims. In this work, we investigate the environment of HL/XZ Tau, which contains a compact and very active nest of YSOs. We explore the kinematic properties of the close association of jets in this region and study the interaction of jets with the ambient medium, as well as the outflows with each other. Methods. We present scanning Fabry-Perot interferometry of the HL/XZ Tau region in Ha and [S II] 6716 angstrom emission. We also measure the proper motions of the knots in the outflows, as derived from images obtained in 1997 and 2001, to achieve the full 3D kinematic picture. Results. Radial velocities of the HL Tau jet indicate a fast spine of low excitation surrounded by a slower sheared sheath of higher excitation. Proper motions range from 200-220 km s(-1) in the HL Tau jet and are aligned within 10 degrees of the jet spine. In combination, the proper motions and radial velocities indicate that three outflows in this region may be interacting with each other. Evidence of an outflow associated with LkH alpha 358 is found, and we suggest it is a source of Herbig-Haro (HH) knots that lie to the southeast of HL Tau and HH 265. Conclusions. We conclude that the southern lobe of the XZ Tau wind disrupts the eastern lobe of the collimated outflow from LkHa 358. The jet emerging from HL Tau is deflected by the northern lobe of the wind from XZ Tau. We propose several probable explanations for the unusual structure of the HL Tau jet. It is plausible that the shocks in the jet spine are maintained by the ram pressure of a low-density crosswind from XZ Tau. The crosswind interacts to form a sheath of entrained gas.