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The interaction of young stars with their environments - HELIXINTAS PROJECT 287: FINAL REPORTPROJECT PERIOD: June 2001 - May 2003 COORDINATOR: Michael D. Smith, Armagh Observatory, College Hill, Armagh, N. Ireland, U.K. CONTACT: 00-44-28-3752-2928 (fax: 00-44-28-3752-7174), email: mds@arm.ac.uk SUMMARY OF RESULTS AND KEY REFERENCES Advances in astrophysics are reliant on well-equiped telescopes. As a result of INTAS support, we were able to update instrumentation on the Byurakan and Special Astrophysical Observatory telescopes. This benefitted this project and maintains our capability to compete internationally in the fututre. We decided to target galactic fields containing weak reflection nebulae, evidence for outflows and evidence for helical structure. Many new observational results were obtained. On studying one nebula of interest, designated RNO127 in Cygnus, we discovered a remarkable change in appearance of nearby structure. We also discovered many new impact regions called Herbig-Haro objects in the extended environment. We pursued our study, making follow-up observations at longer wavelengths (near infrared) and found that we were dealing with a large and active star formation region. These results indicate that star formation is ongoing in many places and not just confined to giant clouds and dark isolated clouds. Further optical observations have also revealed that the IR-nebula is powered by an embedded young variable star. The nature of R Mon has interested astronomers for many decades. We observe an evacuated funnel-shaped cavity, making it a prototypical "cometary nebula" through illumination of the cavity walls. We presented results derived, from our latest spectroscopic capabilities, for the nature of the jet of gas which cuts through the cavity. There is strong evidence for a helical structure, suggesting a combination of a precessing jet with a rotating or transverse-sheared outer cavity. We have also obtained fascinating spectroscopic results (Fabry-Perot scanning interferometry) for several outflows, such as those from HL/XZ Tau in the Taurus star-forming cloud and the bow shock HH83. The radial velocity structures allow us to distinguish and describe components and provide a deeper understanding of how young stars drive jets into their environments (in preparation). In order to interpret the impact regions, we need to improve our modelling of shock waves. One model explores the physics and geometry of the shocks when running into a mixture of molecules and atoms in the environment. We compared the predictions to previously-obtained near-infrared data for the well-studied Herbig-Haro Object HH7, and conclude that the magnetic field is critical to the nature of the shock. We have also looked at another outflow in a bright-rimmed cloud called L1616 in the Orion region. We find here that the new stars form sequentially, after being triggered by the impact of winds from stars of high mass. Computer simulations may provide a bridge between our observations of helical structure and the underlying physical flow. We have applied our simulation code ZEUS-3D to the problem of precessing jets. The difficulties lie in the three dimensional nature of such flows and the complex cooling and chemistry involved. Taking wide-angle and fast precession, we have explored the resulting signatures and found which observational tracers are best to employ. A second study is now underway in which slow precession is investigated. The results are contrasting, with long thin streamers predicted. Our results have an important bearing on how protostars interact with their environments. A major problem in our field is how to eject the angular momentum in order that a cloud can collapse into a star. We have thus presented our results very quickly at conferences. Other groups are also now looking for the possible influence of rotation, shear and precession on jet properties using larger telescopes. Nevertheless, we have been able to make our contribution by providing high quality spectroscopic details. RESULTING PUBLICATIONS are here. |
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