Compression of Interstellar Clouds in Spiral Density-Wave Shocks
Abstract
The results of computer simulations of a mechanism of triggering star formation by galactic shocks are discussed. A spherical 'standard' interstellar cloud passes through a spiral arm shock in the surrounding isothermal gas with resultant flattening over the course of 3 million to 9 million years. The isothermal equation of state used for the intercloud gas results in a supersonic flow of this gas around the cloud, which, together with the effective numerical viscosity of the boundary treatment, causes the Kelvin-Helmholtz instability to be suppressed. Greatly accelerated expansion into the low-pressure intercloud region causes rapid growth of the Rayleigh-Taylor instability and the eventual breakup of the sheet. The shock-driven implosion of a cloud upon entering a spiral arm provides a means of obtaining a first generation of stars at one end of the cloud, which may then cause a sequential star formation chain reaction driven by ionizing radiation or by supernova shocks.
- Publication:
-
The Large-Scale Characteristics of the Galaxy
- Pub Date:
- 1979
- Bibcode:
- 1979IAUS...84..159W
- Keywords:
-
- Astrophysics;
- Density Wave Model;
- Interstellar Gas;
- Stellar Evolution;
- Astronomical Models;
- Compressibility Effects;
- Computerized Simulation;
- Equations Of State;
- Gas Flow;
- Hydrogen Clouds;
- Isothermal Processes;
- Supernovae;
- Supersonic Flow;
- Astrophysics