The Large-Scale Distribution of Interstellar Matter in the Context of the Density-Wave Theory

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.

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Neutral hydrogen in the Sagittarius and Scutum spiral arms

Symposium - International Astronomical Union ◽

10.1017/s0074180900000942 ◽

1970 ◽

Vol 38 ◽

pp. 397-414 ◽

Cited By ~ 3

Author(s):

W. B. Burton ◽

W. W. Shane

Keyword(s):

Large Scale ◽

Galactic Center ◽

Density Wave ◽

Neutral Hydrogen ◽

Wave Theory ◽

Galactic Rotation ◽

Circular Rotation ◽

Kinematic Models ◽

Density Wave Theory ◽

Galactic Longitude

Observations of the neutral hydrogen in the first quadrant of galactic longitude have been analysed. The existence of large-scale streaming motions such as the streaming associated with the Sagittarius arm makes interpretation of the observations in terms of circular galactic rotation unsatisfactory. It is shown that application of the density-wave theory formulated by Lin et al. (1969) leads to a more satisfactory interpretation. Using kinematic models based on this theory the distribution and motion of the neutral hydrogen are studied. Failures of kinematic models based on circular rotation are pointed out. A map of the distribution of neutral hydrogen is produced. The Scutum arm is composed of inner and outer arcs both of which seem to be moving outward from the galactic center with velocities of the order of 30 km s−1.

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Interpretation of large-scale spiral structure

Symposium - International Astronomical Union ◽

10.1017/s0074180900000929 ◽

1970 ◽

Vol 38 ◽

pp. 377-390 ◽

Cited By ~ 4

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.

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

Symposium - International Astronomical Union ◽

10.1017/s0074180900026875 ◽

1974 ◽

Vol 60 ◽

pp. 551-572 ◽

Cited By ~ 1

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.

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