Optically thick Herbig-Haro jets in photoionized regions

¹ Instituto de Astronomía, UNAM, Apartado Postal 70-264, 04510 D. F., México e-mail: masciadri@astroscu.unam.mx
² Instituto de Ciencias Nucleares, UNAM, Apartado Postal 70-543, 04510 D. F., México

Corresponding author: E. Masciadri, elena@astroscu.unam.mx

Received: 23 May 2001
Accepted: 16 July 2001

Abstract

Over the last few years, a number of Herbig-Haro (HH) jets have been discovered within the confines of H II regions. These jets apparently are ejected from low mass stars that are similar to the sources of other "normal" HH jets, but the flows show some special characteristics which are a result of the photoionization due to the ionizing photons emitted by the star that excites the H II region. In this paper, we present HH jet models including an external, photoionizing radiation field, and study the effects of increasing ionizing photon fluxes on the structure of the head of the jet. We find that the morphology, the emission line fluxes and the line ratios change drastically as a function of increasing . These results give general guidelines for deciding whether an HH jet actually does lie within an H II region, based on the morphology and spectroscopic characteristics of the object.