Dynamical evolution of substructure in mollecular clouds
There is abundant and diverse evidence that clumping is a common feature of molecular clouds. These observations have motivated a dynamical model of molecular clouds which views them as an ensemble of interacting clumps of gas. In this work, the primitive forms of clump interaction have been studied through the technique of hydrodynamical simulation. The simplest interaction is that of a single clump plowing through an ambient medium. Plowing clumps in both subsonic and supersonic regimes with particular emphasis on the physics of shock compression and rarefaction, vorticity, and drag have been studied. Also the infrared emission spectra of the shock-heated gas associated with supersonic clumps have been calculated. It is found that an ensemble of clumps will emit radiation, primarily in clump wake, sufficient to be observable. The observation of this infrared radiation as a consistency test of clumpy models of molecular clouds has been proposed. Gravitational instability and clump coalescence have been studied in simulations of clump collisions. The results indicate that gravitational instability is promoted only in collisions between clouds with density contrast on the order of unity. The relationship between instability and coalescence is discussed, and it is argued that most collisions will lead to clump disruption and dispersal. The implications for the efficiency of star formation has been noted. The thermal stability of molecular gas has also been studied, and unstable condensation modes in secularly cooling gas have been found. These modes damp before reaching nonlinearity, but provide a continual source of acoustic perturbation.
- Research Organization:
- Texas Univ., Austin (USA)
- OSTI ID:
- 7001780
- Resource Relation:
- Other Information: Thesis (Ph. D.)
- Country of Publication:
- United States
- Language:
- English
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Related Subjects
GENERAL PHYSICS
COSMIC GASES
MORPHOLOGY
COLLISIONS
EMISSION SPECTRA
HEATING
HYDRODYNAMICS
INFRARED RADIATION
MATHEMATICAL MODELS
MOLECULES
SHOCK WAVES
SIMULATION
STABILITY
ELECTROMAGNETIC RADIATION
FLUID MECHANICS
FLUIDS
GASES
MECHANICS
RADIATIONS
SPECTRA
640105* - Astrophysics & Cosmology- Galaxies