scholarly journals ON THE SPIRAL STRUCTURE OF DISK GALAXIES, II. OUTLINE OF A THEORY OF DENSITY WAVES

1966 ◽  
Vol 55 (2) ◽  
pp. 229-234 ◽  
Author(s):  
C. C. Lin ◽  
F. H. Shu
Keyword(s):  
Spiral Structure ◽  
Disk Galaxies ◽  
Density Waves

Density waves in disk galaxies

1967 ◽  
Vol 31 ◽  
pp. 313-317 ◽  
Author(s):  
C. C. Lin ◽  
F. H. Shu
Keyword(s):  
Mathematical Analysis ◽  
Spiral Structure ◽  
Stellar System ◽  
Collective Modes ◽  
Disk Galaxies ◽  
Spiral Pattern ◽  
Density Waves ◽  
The Galaxy ◽  
Detailed Mathematical Analysis

Density waves in the nature of those proposed by B. Lindblad are described by detailed mathematical analysis of collective modes in a disk-like stellar system. The treatment is centered around a hypothesis of quasi-stationary spiral structure. We examine (a) the mechanism for the maintenance of this spiral pattern, and (b) its consequences on the observable features of the galaxy.

scholarly journals Numerical Experiments on the Response Mechanism of Barred Spirals

1983 ◽  
Vol 100 ◽  
pp. 207-208
Author(s):  
K. O. Thielheim ◽  
H. Wolff
Keyword(s):  
Numerical Experiments ◽  
Spiral Structure ◽  
Stellar Disk ◽  
Disk Galaxies ◽  
Density Waves ◽  
First Order ◽  
Spiral Density Waves ◽  
Stellar Component ◽  
Spiral Structures ◽  
Self Gravity

As a generating mechanism of spiral structure, we have recently studied the driving of density waves in the stellar component of disk galaxies by growing barlike perturbations or oval distortions. Numerical experiments (Thielheim and Wolff 1981, 1982) as well as analytical calculations using the first-order epicyclic approximation (Thielheim 1981; Thielheim and Wolff 1982) have been performed, demonstrating that this mechanism is capable of producing two-armed trailing spiral density waves in disks of noninteracting stars. These regular, global spiral structures are similar to those found in N-body experiments on self-consistent stellar disks that show bar instabilities which are weak enough to allow spiral patterns to persist (e.g., Hohl 1978; Berman and Mark 1979; Sellwood 1981). On account of this similarity, we take the view that the spiral structure observed in N-body experiments is primarily not an effect of the self-gravity of the stellar disk but a response phenomenon, caused by the formation of a weak central bar and its subsequent growth due to angular momentum extraction by interaction with the spiral as described by Lynden-Bell and Kalnajs (1972).

Dynamical imprint of interstellar gas on persistence of spiral structure in galaxies

2017 ◽  
Vol 13 (S334) ◽  
pp. 296-297
Author(s):  
Soumavo Ghosh ◽  
Chanda J. Jog
Keyword(s):  
Time Scale ◽  
Spiral Structure ◽  
Density Wave ◽  
Disk Galaxies ◽  
Interstellar Gas ◽  
Spiral Arms ◽  
Pattern Speed

AbstractThe persistence of the spiral structure in disk galaxies has long been debated. In this work, we investigate the dynamical influence of interstellar gas on the persistence of the spiral arms in disk galaxies. We show that the gas helps the spiral arms to survive for longer time-scale (~ a few Gyr). Also, we show that the addition of gas in calculation is necessary for getting a stable density wave corresponding to the observed pattern speed of the spiral arms.

scholarly journals Selfpropagating Stochastic Star Formation and Spiral Structure

1983 ◽  
Vol 100 ◽  
pp. 141-142 ◽  
Author(s):  
J. V. Feitzinger ◽  
P. E. Seiden
Keyword(s):  
Star Formation ◽  
Spiral Structure ◽  
Relative Importance ◽  
Formation Model ◽  
Density Waves ◽  
Spiral Density Waves ◽  
Two Component ◽  
Grand Design ◽  
Dynamic Phenomena

Spiral structure in galaxies can arise from both dynamic and non dynamic phenomena: spiral density waves and stochastic selfpropagating star formation. The relative importance of these effects is still not known. Deficiences of the original selfpropagating star formation model (where only stars are taken into account) are overcome by explicitly considering the stars embedded in and interacting with a two-component gas (Seiden and Gerola, 1979; Seiden, Schulman and Feitzinger, 1982; Seiden and Gerola, 1982). The two-component gas is essential because it is the means by which we get feedback in the interaction between stars and gas. The coupling between stars and gas regulates and stabilizes star formation in a galaxy. Under proper conditions this model can give good grand design spirals (Fig. 1).

scholarly journals Spiral Structure: Density Waves or Material Arms?

1983 ◽  
Vol 100 ◽  
pp. 161-162 ◽  
Author(s):  
S. V. M. Clube
Keyword(s):  
Stationary Distribution ◽  
Globular Cluster ◽  
Spiral Structure ◽  
The Sun ◽  
Density Waves ◽  
Structure Density

Recent studies (Frenk and White 1980, 1982) of the (x, y, z) and (Π, θ) distributions of the Galactic globular cluster population have given Ro = 6.8±0.8 kpc and Π = 51±26 kms−1 for the inner halo. The observations leading to these solutions are well illustrated by the ρ vs. x plot in figure 1 (Clube and Watson (CW), 1979) for the globulars with the best determined data within |l|, |b| < 20°. The independently determined Ro value clearly divides the distribution in such a way that most of the objects on the nearside of the G.C. approach the Sun while those on the farside recede, the probability that this arrangement arises by chance from a “stationary” distribution being ~ 0.002.

scholarly journals Shells, Ripples and Tails

1999 ◽  
Vol 186 ◽  
pp. 165-172
Author(s):  
D. Carter
Keyword(s):  
Spiral Structure ◽  
Morphological Features ◽  
Disk Galaxies ◽  
Tidal Tails

It has been known since the early simulations of Wright (1972), and Toomre & Toomre (1972), that interactions between galaxies can give rise to quite spectacular morphological features, including spiral structure in disk galaxies, and extensive tails. It appears that long tidal tails only arise from interactions involving disk galaxies (Toomre & Toomre 1972), and thus the presence of two opposed long tidal tails in a number of disturbed galaxies such as the Antennae (Whitmore & Schweizer 1995), NGC 3921 (Schweizer 1996), and NGC 7252 (Schweizer 1982), has led to the interpretation of these galaxies as disk-disk mergers in progress. These systems can be modeled rather successfully, as the work of Hibbard & Mihos (1995) has shown.

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