IR diagnostics of embedded jets: kinematics and physical characteristics of the HH46-47 jet

摘要

Context. We present an analysis of the kinematics andphysical properties of the ClassI driven jet HH46-47 based on IRmedium and low resolution spectroscopy obtained with ISAAC on VLT. Aims. Our aim is to study the gas physics as a function of thevelocity and distance from the source and to compare the results withsimilar studies performed on other ClassI and classical T Taurijets as well as with existing models for the jet formation andexcitation. Methods. The ratios and luminosities of several important diagnostic lines (e.g. [Fe II]1.644, 1.600m, [P II]1.189m, and H2lines) have been used to derive physical parameters such as electron density, H2 temperature, iron gas-phase abundance and mass flux. [Fe II]1.644m and H22.122mposition velocity diagrams (PVDs) have been additionally constructed tostudy the kinematics of both the atomic and molecular gas. Results. Within 1000-2000AU from the source the atomic gas presents a wide range of radial velocities, from -230kms-1 to 100kms-1. Only the gas component at the highest velocity (high velocity component, HVC) survives at large distances. The H2 shows only a single velocity component at almost zero velocity close to the source while it reaches higer velocities (up to 95kms-1) further downstream. Electron densities ()and mass ejection fluxes ()have been separately measured for the HVC and for the component at lower velocity (LVC) from the [Fe II] lines. increases with decreasing velocities with an average value of cm-3 for the LVC and 4000cm-3 for the HVC, while the opposite occurs for which is yr-1 and yr-1 for the HVC and LVC, respectively. The mass flux carried out by the molecular component, measured from the H2 lines flux, is yr-1. We have estimated that the Fe gas phase abundance is significantly lower than the solar value, with 88% of iron still depleted onto dust grains in the internal jet region. This fraction decreases to 58%, in the external knots. Conclusions. Many of the derived properties of theHH46-47jet are common to jets from young stellar objects (YSOs)in different evolutionary states. The derived densities and mass fluxvalues are typical of ClassI objects or very active T Tauristars. However, the spatial extent of the LVC and the velocitydependence of the electron density have been so far observed only inanother ClassI jet, the HH34jet, and are not explained bythe current models of jet launching. Key words: circumstellar matter - Herbig-Haro objects - ISM: jets and outflows - ISM: individual objects: HH46-47 - infrared: ISM