Other
Scientific paper
Jun 2001
adsabs.harvard.edu/cgi-bin/nph-data_query?bibcode=2001phdt.........5d&link_type=abstract
Thesis (PhD). THE UNIVERSITY OF ROCHESTER, Source DAI-B 61/12, p. 6514, Jun 2001, 171 pages.
Other
Scientific paper
We explore the Generalized Wind Blown Bubble (GWBB) paradigm and its ability to explain the morphology of a few classes of objects: Young Stellar Object (YSO) molecular outflows, FU Orionis (time dependent wind) outflows, and Proto Planetary Nebulae (PPNe). These objects represent stages at opposite ends of a stellar lifecycle. We apply two-dimensional hydrodynamic simulation to follow the non-linear evolution of interactions between the circumstellar winds and surrounding environments. The simulations include the effects of atomic and molecular cooling microphysics, stellar gravity, and angular momentum. Synthetic observations are produced from the simulation data and compared to contemporary object observations. Using parameters relevant for YSO molecular outflows, we analyze how the variation in the balance of ram pressure between wind and infalling ambient gas affects the morphology of the resulting outflows. Assuming non- spherical cloud collapse, we find that relatively strong winds can carve out wide, conical outflow cavities and that relatively weak winds can be strongly collimated. If the winds become weak enough, they can be cut off entirely by the infalling environment. We investigate the interaction of multi-stage winds in a proto-planetary nebula, namely those of a pulsed slow wind, a medium velocity wind in the shape of a circumstellar torus, and a final fast wind. The results are compared closely with the well studied object CRL2688 (Egg Nebula). Comparisons to other nebulae are also made. Using several arrangements for the winds and applying synthetic observations it is found that it is difficult to recover the shape of CRL2688 if the final stage fast wind is not precollimated. More complicated dynamics or magnetic fields are suggested to resolve the discrepancy in that case. An examination is made of the interaction of a pulsing wind with an infalling environment. The hydrodynamic simulations are motivated by the FU Orionis and EXor classes of YSOs, which are observed to burst periodically. Results are compared with the earlier steady wind models. Several effects of the time- dependence are noted including the collapse of converging flows near the pole, the self-shocking features of the stellar wind, and the formation of a polar collimation channel.
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