The Spatial Distribution of Ultraviolet Line and Continuum Emission in Herbig-Haro Objects

Abstract

Using archival IUE data and "monochromatic" CCD images in the optical range, the authors compare the spatial distribution of ultraviolet and optical emission in Herbig-Haro objects. Specifically, they consider the objects HH 1, HH 2, HH 24, HH 32, HH 43, and HH 47. Spatial distributions have been studied in the UV lines C IV 1550, C III] 1909, C II] 2326, and Mg II 2800. They have been compared to the distributions of some optical lines. The distributions of the continuum emission in the short- and long-wavelength ranges of IUE have also been studied. The following results have been obtained: (1) For all six objects studied, the observed UV radiation really originates in the objects themselves. (2) As expected, the C IV and C III] emission regions are small. (3) The continuum in the IUE short-wavelength range always shows a distribution that is broader than that of any measured line emission in the ultraviolet or optical range. The continuum distribution in the IUE long-wavelength range, on the other hand, is quite narrow and comparable to the optical continuum distribution. This probably indicates that while in the optical and the long-wavelength IUE range the continuum is essentially a pure two-photon continuum, an additional continuum-formation mechanism (e.g., fluorescent H₂ emission) is present in the short-wavelength range.