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**Session 42 - Molecular Clouds: Models and Observations.**

*Display session, Tuesday, June 11*

*Great Hall, *

## [42.01] Numerical Simulation of Self-gravitational Instability of Isothermal Gaseous Slab Under High External Pressure

*S. Miyaji, M. Umekawa, R. Matsumoto (Chiba Univ.), T. Yoshida (Ibaraki Univ.)*
Gaseous slab is formed with shock waves from super novae, collision
of interstellar clouds, etc.
When the mass in the Jeans scale is more than Jeans mass, the slab
fragments into many clumps by gravitational instability. But in high
external pressure environment, even the slab which is stable against
Jeans mode can fragment(Elmegreen and Elmegreen 1978).This phenomenon
results from incompressible mode instability(Lubow and Pringle 1993).
These works are by linear analysis.
We study numerically this isothermal gaseous slab which is formed by
high external pressure and whose thickness is much smaller than its
scale height. We assume self-gravitational fluid, and use two dimensional
flux split method. Our model size is taken about the scale of linear
maximum growth rate wave length and its five times length, which is an
example of much longer than the maximum growth rate wave length.
When the incompressible mode instability takes place, it becomes
clumps. Each mass of the clumps is less than the Jeans mass. Then the
clumps approach each other by gravitational interaction to form bigger
clumps.
In the presentation we will show results of numerical simulation and
discuss about the interaction of fragments on star formation or initial
mass function.

**Program
listing for Tuesday**