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 ~ 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 and compare these values with those derived from observations using the sulfur doublet to constrain the electron density.

Time-dependent MHD shocks and line emission: the case of the DG Tau jet

S. Massaglia;A. Mignone;
2005-01-01

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 ~ 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 and compare these values with those derived from observations using the sulfur doublet to constrain the electron density.
2005
Inglese
Esperti anonimi
442
549
554
6
ISM: jets and outflows; magnetohydrodynamics (MHD); hydrodynamics; stars: early-type
no
1 – prodotto con file in versione Open Access (allegherò il file al passo 5-Carica)
262
3
S. Massaglia; A. Mignone; G. Bodo
info:eu-repo/semantics/article
open
03-CONTRIBUTO IN RIVISTA::03A-Articolo su Rivista
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Utilizza questo identificativo per citare o creare un link a questo documento: https://hdl.handle.net/2318/57701
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