Time-Dependent MHD Shocks and Line Emission: The Case of the DG Tau Jet

Abstract

The line emission from a growing number of Herbig-Haro jets can be observed and resolved at angular distances smaller than a few arcseconds from the central source. The interpretation of this emission is problematic, since the simplest model of a cooling jet cannot sustain it. It has been suggested that what one actually observes are shocked regions with a filling factor of $\sim 1$. In this framework, up to now, comparisons with observations have been based on stationary shock models. Here we introduce for the first time the self-consistent dynamics of such shocks and we show that considering their properties at different times, i.e. locations, we can reproduce observational data of the DG Tau microjet. In particular, we can interpret the spatial behavior of the [SII]6716/6731 and [NII]/[OI]6583/6300 line intensity ratios adopting a set of physical parameters that yield values of mass loss rates and magnetic fields consistent with previous estimates. We also obtain the values of the mean ionization fraction and electron density along the jet, compare these values with the ones derived from observations using the sulfur doublet to constrain the electron density (e.g. Bacciotti et al. 1995).

arXiv comment6 pages, 3 figures

References in corpus (3)

• HST/STIS spectroscopy of the optical outflow from DG Tau: structure and kinematics on sub-arcsecond scales
• Heating and Ionization of X-Winds
• On the Influence of Magnetic Fields on the Structure of Protostellar Jets

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• Time Variability of Emission Lines for Four Active T Tauri Stars (I): October--December in 2010
• Numerical simulations of radiative magnetized Herbig-Haro jets: the influence of pre-ionization from X-rays on emission lines
• Young stellar object jet models: From theory to synthetic observations
• Time-dependent MHD shocks and line intensity ratios in the HH 30 jet: A focus on cooling function and numerical resolution
• Proper motions of radiative knots in simulations of stellar jets - An alternative to pulsating inflow conditions