Meeting update -- Rotation

The product of initial central angular velocity with the free fall time, as measured from the central density of the clump — omega*tff, can be used as a parameter for the rotation problem. Authors ​Matsumoto & Hanawa ('03) have found that when this product is low enough to allow collapse, but larger than ~ 0.05 (when a disk can form before first core formation), the clump fragments into a particular morphology. When the BE sphere is critical, with a small density "enhancement", SLOW rotation induces collapse.

These authors initialize angular velocity with the following:

This perturbs the amplitude of the global rotation,

with varying amplitudes of Omega2 and Omega3, the m=2 and m=3 velocity perturbations. The parameter C determines the angular velocity's dependance on r. For C=0, rotation is rigid-body, for C larger, Omega decreases more rapidly with increasing r. Both C and beta, the ratio of rotational to gravitational energy strongly determine the resulting morphology of collapse — the fragmentation into bars, discs, etc.

The authors ​Banerjee, Pudritz, Holmes on the other hand study the collapse of both high mass and low mass BE spheres. There initial conditions prescribe a rigid body rotation that is also determined by the product Omega*tff. They use this parameter = 0.1, 0.2, 0.3. They go through the calculation of both alpha (thermal/gravitational energy) and beta (rotational/gravitational energy) of BE spheres and explain that beta is maximum at the OUTER edge of the cloud.

My questions are —

1) Rigid body vs. keplerian rotation? What conditions for each rotation? If we start out with rigid body, do we expect the collapse to evolve to a keplerian rotation?

2) Why does slow rotation trigger collapse rather than expansion or nothing? How does alpha and beta change with r and contribute to the total stability of the clump? How does the speed of rotation effect stability?

3) A good way to visualize the simulation output?

4) Initial conditions for the BE sphere — should the set-up be one that is JUST critical, but doesn't collapse? Or should it be a set-up that is already super-critical (thermal energy reduced in grid by 10%)?

Current Run:

Is in the queue in BH

It has:

-An omega*tff = 0.1 (rigid body rotation)

-A critical BE sphere (stable at the critical radius)

-Grid is shifted in x,y by ½ dx

-43+1level cells — ~ 20 zones p/clump radius

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