Changes between Version 17 and Version 18 of u/BonnorEbertMatched2

Timestamp:

10/15/12 21:53:14 (12 years ago)

Author:

Erica Kaminski

Comment:

—

u/BonnorEbertMatched2

@@ -5 +5 @@
 '''Abstract'''
 
-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. [The ram pressure was calculated at the sphere's outer edge and indeed exceeded the critical threshold of external pressure on the BE sphere. However, Pram>Pcrit long after Pthermal>Pcrit, thus it seems the increase in thermal pressure was 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 those found previously by authors such as who found a very nice outside-in collapse. 
+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 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?).
 
--[Results should go here, but not sure if this is the line of reasoning we want to follow]
 -Maybe add something about Hannebelle et al. here, describe the collapse more clearly as triggered by a compression wave?
--Add to the list of runs the 10% overdensity case -- B&P run?
--Should we run these same set-ups, but with a sub-critical sphere?
+
 
 '''Introduction Outline'''
 
-I. Classic outside-in collapse features vs. SIS
+I. Classic outside-in collapse features vs. SIS (singular isothermal sphere)
 i. Relation to star formation
 ii. BE sphere definitions
@@ -26 +24 @@
 ii. The code/the model
 V. Thesis Paragraph
-The collapse of the isothermal, hydrostatic sphere has been studied extensively, albeit with focus mainly on 2 special cases: the self-similarity solutions of the collapsing singular isothermal sphere (Shu), and the more modern numerical studies of collapsing marginally stable spheres (F&C, B&P). However, the latter, and today generally more popular, simple model for protostar formation has been largely limited to the placement of a critical BE sphere in an ambient medium that was a) in pressure equilibrium with the sphere, b) of uniform density many times lighter than that of the sphere’s outermost edge, and c) perturbed out of equilibrium by some artificial trigger such as an overdensity of the sphere and surrounding medium. This led to the present objective of exploring the effect of whether collapse of a marginally stable sphere could be induced by its environment with no ad hoc perturbations, and how that collapse may differ from previous qualitative features. 
+The collapse of the isothermal, hydrostatic sphere has been studied extensively, but mainly with focus on 2 special cases: the self-similarity solutions of the collapsing singular isothermal sphere (Shu), and the more modern numerical studies of collapsing marginally stable Bonnor Ebert spheres (F&C, B&P). The latter, relevant here and the generally more acceptable simple model for protostar formation, has been limited to the placement of a critical BE sphere in an ambient medium that was a) in pressure equilibrium with the sphere, b) of uniform density many times lighter than that of the sphere’s outermost edge, and c) perturbed out of equilibrium by some artificial trigger such as an overdensity of the sphere and surrounding medium. This led to the present objective of exploring the effect of whether collapse of a marginally stable sphere could be induced by its environment with no ad hoc perturbations, and how that collapse may differ from previous qualitative features. 
 
 '''Methods Outline'''