Application of the Density-Wave Theory to the Spiral Structure of the Milky way System. III. Magnetic Field: Large-Scale Hydromagnetic Shock Formation

1970 ◽  
Vol 161 ◽  
pp. 887 ◽  
Author(s):  
William W., Jr. Roberts ◽  
C. Yuan
Keyword(s):  
Magnetic Field ◽  
Large Scale ◽  
Milky Way ◽  
Spiral Structure ◽  
Density Wave ◽  
Wave Theory ◽  
Shock Formation ◽  
Density Wave Theory

scholarly journals Interpretation of large-scale spiral structure

1970 ◽  
Vol 38 ◽  
pp. 377-390 ◽  
Author(s):  
C. C. Lin
Keyword(s):  
Large Scale ◽  
Spiral Structure ◽  
Density Wave ◽  
Wave Theory ◽  
Point Of View ◽  
Spiral Form ◽  
Empirical Point ◽  
Density Wave Theory ◽  
Semi Empirical ◽  
General Explanation

The present paper consists of three parts: (1) A general explanation, from a semi-empirical point of view, of the density wave theory and its ramifications, with only a few remarks on those detailed features which have not been stressed before; (2) a statement of our conclusions about the Milky Way System; and (3) a discussion of the problem of the origin of density waves of spiral form.

scholarly journals Current Problems in 21 cm Line Studies of the Large-Scale Structure of the Galaxy

1974 ◽  
Vol 60 ◽  
pp. 551-572 ◽  
Author(s):  
W. B. Burton
Keyword(s):  
Shock Front ◽  
Large Scale ◽  
Spiral Structure ◽  
Density Wave ◽  
Model Fitting ◽  
Neutral Hydrogen ◽  
Wave Theory ◽  
Large Scale Structure ◽  
The Galaxy ◽  
Density Wave Theory

A number of current problems in 21 cm line studies of the Galaxy as a whole are discussed. Because of the difficulties involved with straightforward mapping, it is important to isolate integrated and other properties of the hydrogen profiles, the interpretation of which does not require accurate distance determinations. In addition, methods of analysis are necessary which either account for or exploit the sensitivity of hydrogen profiles to velocity irregularities and to geometrical configurations. The model-fitting approach to the interpretation of the hydrogen profiles is useful in this respect. Extragalactic hydrogen studies which show the relative ordering of the various components of spiral structure can inspire research in our own Galaxy. Such investigations are necessary for an understanding of the forces governing the spiral structure. It seems that the neutral hydrogen is primarily a tracer of locations where the overall distribution of stars is producing a gravitational sink. Other spiral tracers, in particular the molecules, are better considered as tracers of regions where the gas has been compressed, perhaps (at least on a large scale) by the shock front predicted by the density-wave theory.

scholarly journals Dynamics of the Gas in Spiral Galaxies

1977 ◽  
Vol 45 ◽  
pp. 11-30 ◽  
Author(s):  
William W. Roberts
Keyword(s):  
Observational Studies ◽  
Large Scale ◽  
Density Wave ◽  
Wave Theory ◽  
Relative Distribution ◽  
Star Forming ◽  
Molecule Formation ◽  
Gaseous Component ◽  
Density Wave Theory ◽  
Co Observations

AbstractThe dynamics of the gaseous component in disk-shaped galaxies is thought to play an important governing role in star formation, molecule formation, and the degree of development of spiral structure. The prospect that density waves and galactic shock waves are present on the large-scale has received support in recent years from a variety of observational studies. Large-scale shocks provide a most promising mechanism for driving star-forming and molecule-forming events on the scales of many kpc along spiral arms. Such shocks may also govern the kinematics and relative distribution of various galactic tracers. This is particularly apparent in M81 and other external spirals, because of our “bird’s-eye-view” perspective, and for the tracers of HI and CO in our own Galaxy. Comparison of the CO observations with model simulations based on the precepts of the density wave theory shows that these precepts are supported by several observational results.

scholarly journals Enhanced galactic star formation as caused by the Milky Way - Large Magellanic Cloud interaction: an experience from density wave studies

1991 ◽  
Vol 148 ◽  
pp. 440-440
Author(s):  
L. S. Marochnik ◽  
A. A. Suchkov
Keyword(s):  
Star Formation ◽  
Milky Way ◽  
Formation Rate ◽  
Density Wave ◽  
Wave Theory ◽  
Large Magellanic Cloud ◽  
Magellanic Cloud ◽  
Gas Flows ◽  
Andromeda Nebula ◽  
Density Wave Theory

Star formation in interacting galaxies is usually strongly enhanced. The star formation rate in the Milky Way is substantially greater than, for example, in the Andromeda Nebula. A plausible cause for this difference may be the interaction of the Milky Way with the Large Magellanic Cloud. We suggest that one of the possibilities for this may be the enhanced formation of cold gas clouds as the gas flows through the gravitational potential well of a tidal wave caused by the interaction; another contribution may come from compression of pre-existing clouds when they pass this way. This scenario is obviously quite similar to that envisioned in “frames” of the density-wave theory.

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