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The Ionization State along the Beam of Herbig-Haro Jets

Published online by Cambridge University Press:  25 May 2016

Francesca Bacciotti
Francesca Bacciotti*
Affiliation:
Dipartimento di Astronomia e Scienza dello Spazio, Università di Firenze, Largo E. Fermi 5, 50125 Firenze, Italy

Abstract

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An original spectroscopic diagnostic technique has been recently developed that allows to estimate in a model-independent way the ionization fraction xe and the average excitation temperature in the beam of Herbig-Haro jets (Bacciotti, Chiuderi and Oliva 1995). The procedure is based on the fact that in the low excitation conditions present in this region the ionization state of oxygen and nitrogen can be assumed to be regulated by charge exchange with atomic hydrogen. The application of this technique to long-slit spectra of several well-known stellar jets indicates that the hydrogen ionization fraction xe starts from 0.2-0.4 at the beginning of the flow and gently decreases along the whole jet or along sections of it as a result of time-dependent recombination. The average temperature stays almost constant, ranging from 4500 to 7000 K. The momentum transfer rates evaluated with the derived total number densities (nH ∼ 103–104 cm–3) give support to the picture in which the jet is responsible for the acceleration of a surrounding molecular outflow.

Type
I. Herbig-Haro Objects, H2 Flows and Radio Jets
Information
Symposium - International Astronomical Union , Volume 182: Herbig-Haro Flows and the Birth of Low Mass Stars , 1997 , pp. 73 - 82
Copyright
Copyright © Kluwer 1997 

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