Doctor of Philosophy
Department of Engineering Physics
Mader, Stacy Lyall, Giant Herbig-Haro flows: identification and consequences, Doctor of Philosophy thesis, Department of Engineering Physics, University of Wollongong, 2001. http://ro.uow.edu.au/theses/1828
Herbig-Haro (HH) objects are the optical components of outflows associated with young stellar objects. Characteristic spectra of HH objects include strong Hα and [SII] emission (6717/6737Å) which arises as the stellar wind from a source impacts with the surrounding interstellar medium. With the discovery that HH flows can attain sizes of a parsec or more, a natural course of action is to determine their distribution in star forming regions and what effect they have on the surrounding interstellar medium. As most known giant HH flows extend up to several degrees on the sky, only the largest CCD imaging cameras can provide the necessary field of view to identify new candidates. Enter the AAO /UKST Hα survey of the Southern Galactic Plane. With its large field of view (4°x4°) and superb imaging resolution (provided by the Hα filter and TechPan emulsion combination), the survey is particularly suited to identifying new HH objects and giant flows in southern star formation regions.
The first part of this thesis aims to determine the effectiveness of widefield material from the ESO/SERC Southern Sky Atlases in characterising HH flows. Comparison of IllaJ, IIIaF and IVN films shows they are extremely useful in characterising HH flows by distinguishing between reflection and emission nebulosity, tracing excitation conditions along a flows length and identifying their energy sources which can range from optically-visible T Tauri stars to deeply embedded Class 0 protostars. We present an ESO/SERC, C C D imaging and IRAS HIRES survey of a number of poorly-studied HH objects which have yet to have their energy source identified. For the majority of surveyed objects, we argue most are part of giant HH flows.
The second part of this thesis utilises AAO/UKST Hα wide-field material to search for giant HH flows in Orion L1630/L1641 and Canis Major OB1/R1. For the Orion region, we find a large number of giant HH flows associated with the L1641-N infrared cluster and one in the Ori I-2 cometary globule. Giant HH flows were also associated with V380 Ori and a Class 0 protostar near NGC 2023. For the Canis Major region, the HH flow from Z CMa was found to be much larger than previously thought. By combining AAO/UKST Hα and 13CO data, we show that for the majority of giant flows in L1630 and L1641, there is at least one large-scale cavity projected against the terminal bow shock of the HH flow. By comparing the location of dense CS cores with respect to these cavities, we suggest that giant HH flows can account for the current and future modes of star formation within L1641.