| 7 | | This paper describes a series of 3D hydrodynamic simulations that explored the effects of placing a marginally stable Bonnor Ebert sphere in different ambient media. Various uniform density media were initialized that were in pressure equilibrium with the Bonnor Ebert sphere. These densities ranged from a traditional light ambient (rho=0.01rho(Rbe)) to an ambient with density that matched that at the sphere’s outermost edge (rho=rho(Rbe)). The main aims were to a) discern whether a massive ambient medium would be sufficient to induce collapse of the sphere, b) whether this collapse would be triggered by the ram pressure of infalling ambient material gravitationally accelerated by the BE sphere, and c) how this collapse would compare with the classic cases of outside-in and inside-out collapse of previous models. [Pram indeed exceeded Pcrit, however, only after Pthermal>Pcrit, thus how to differentiate the primary trigger for collapse?]. In contrast, the sphere in the light ambient medium remained dynamically stable, oscillating slowly about its equilibrium values for ~ 5 crossing times. These results are qualitatively different than that of the outside-in collapse as found by others after perturbing the sphere with a density enhancement (though, they perturbed a sphere in a light ambient -- maybe we should perturb the sphere in a matched ambient - would we recover the outside-in collapse?). |
| | 7 | This paper describes a series of 3D hydrodynamic simulations that explored the effects of placing a marginally stable Bonnor Ebert sphere in different ambient media. Various uniform density media were initialized that were in pressure equilibrium with the Bonnor Ebert sphere. These densities ranged from a traditional light ambient (rho=0.01rho(Rbe)) to an ambient with density that matched that at the sphere’s outermost edge (rho=rho(Rbe)). The main aims were to a) discern whether a massive ambient medium would be sufficient to induce collapse of the sphere, b) whether this collapse would be triggered by the ram pressure of infalling ambient material gravitationally accelerated by the BE sphere, and c) how this collapse would compare with the classic cases of outside-in and inside-out collapse of previous models. [Pram indeed exceeded Pcrit, however, only after Pthermal>Pcrit, thus how to differentiate the primary trigger for collapse?]. In contrast, the sphere in the light ambient medium remained dynamically stable, oscillating slowly about its equilibrium values for ~ 5 crossing times. These results are qualitatively different than that of the outside-in collapse triggered by a density enhancement of the sphere and surrounding medium, as found by Foster and Chevalier '93, and others. (Afterthought: They perturbed a sphere in a light ambient -- maybe we should perturb the sphere in a matched ambient - would we recover the outside-in collapse?). |
