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Models for the Emission-Line Spectra of the Low-Excitation Herbig-Haro Objects

Published online by Cambridge University Press:  04 August 2017

Michael A. Dopita ,
Saul Caganoff ,
Richard D. Schwartz  and
Martin Cohen
Michael A. Dopita
Affiliation:
Mt. Stromlo and Siding Spring Observatories, Australian National University
Saul Caganoff
Affiliation:
Mt. Stromlo and Siding Spring Observatories, Australian National University
Richard D. Schwartz
Affiliation:
Department of Physics, University of Missouri, St. Louis
Martin Cohen
Affiliation:
NASA-Ames Research Center and Radio Astronomy Laboratory, University of California, Berkeley

Abstract

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The class of Low-Excitation Herbig-Haro Objects are characterised by [SII] and [OI] lines which are comparable in strength to H-Alpha, by [NI] lines that are comparable to H-Beta, relatively weak [NII] and [OII] lines, little or no [OIII] emission and a very strong blue-UV “excess”. This blue and UV continuum in low-excitation HH Objects was noted as a problem by Brugel, Böhm and Mannery (1981), Ortalani and D'Odorico (1980) and Böhm, Böhm-Vitense and Brugel (1981). The first suggestion that it results from collisionally enhanced Hydrogen two-photon (2q) continuum was by Dopita (1981). The subsequent observations of Dopita, Binette and Schwartz (1982) proved that this was indeed the case. However, although very close correlations between this enhancement and the emission-line spectrum were found, a fair theoretical description could only be obtained for very youthful shock models with ages of order 30 years. However, there seems to be no reason why low excitation HH shocks should be much younger than the high excitation shocks.

Type
I. Star Forming Processes in the Solar Neighborhood
Information
Symposium - International Astronomical Union , Volume 115: Star Forming Regions , 1987 , pp. 346 - 347
Copyright
Copyright © Reidel 1987 

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