A multiwavelength observational investigation of Herbig-Haro objects and their exciting stars

• Main Author: Stapelfeldt, Karl Roald
• Format: Others
• Language: en
• Published: 1991
• Online Access: https://thesis.library.caltech.edu/3568/1/Stapelfeldt_kr_1991.pdf; Stapelfeldt, Karl Roald (1991) A multiwavelength observational investigation of Herbig-Haro objects and their exciting stars. Dissertation (Ph.D.), California Institute of Technology. doi:10.7907/2638-br68. https://resolver.caltech.edu/CaltechETD:etd-09162008-083954 <https://resolver.caltech.edu/CaltechETD:etd-09162008-083954>

NOTE: Text or symbols not renderable in plain ASCII are indicated by [...]. Abstract is included in .pdf document. Herbig-Haro objects are small optical emission line nebulae, shock-heated by collimated winds from young stars. In this thesis, near-infrared imaging and high resolution optical imaging spectroscopy have been used to investigate Herbig-Haro object shock structure. Four objects have been studied: HH 7-11, HH 12, HH 34, and HH 1. By a detailed comparison of emission line images and spatially complete kinematic maps, we find that although no single flow model can be applied to all regions, some regions do fit the existing models quite well. HH 7 is well-described as the working surface of a stellar jet, with both a bowshock and a jet terminus shock identified within it. The density of this jet is shown to be comparable to the density of the medium it is impacting. Based on the absence of 2[...] H2 line emission in the shocked wind material, H2 does not appear to be a major constituent of the outflowing winds. Where H2 emission is found, the associated [S II] emission tends to have lower radial velocities. The 1.64 [...] [Fe II] emission line has been imaged for the first time in HH objects. The [Fe II] images indicate extinction is not significant in determining the optical appearance of the HH objects studied, and thus the HH 34 bipolar outflow is indeed a one-sided jet system. The kinematics and H2 morphology of HH 12 argue for SVS 12 as this object's exciting star, a conclusion which strongly suggests that the observed proper motions in this object represent pattern motion rather than a material velocity. The second part of this work is a study of the circumstellar material of two HH object exciting stars using millimeter-wave interferometry. High resolution [...]CO images suggest that the HH 34 and HH 111 exciting stars both possess circumstellar disks elongated perpendicular to the highly collimated optical jets emerging from these two sources. The masses of these disks are two to four times greater than the disk masses found for T Tauri stars, although the sizes are comparable. The stellar source masses are most likely less than 2 M[...]. The total weight of evidence argues that HH exciting stars represent an earlier stage of stellar evolution than T Tauri stars, and that large disk masses are being accreted onto the central star, dispersed by the outflow winds, and/or formed into planets during the earliest phases of the life of a star.