scholarly journals Lifetime of density waves and classification of spirals

1979 ◽  
Vol 84 ◽  
pp. 155-156
Author(s):  
J. V. Feitzinger ◽  
Th. Schmidt-Kaler
Keyword(s):  
Density Wave ◽  
Wave Theory ◽  
Density Waves ◽  
Spiral Arms ◽  
Density Wave Theory

Checking the density-wave theory against observations of our own Galaxy has proven very difficult, as witnessed also at this Symposium. Less ambiguous results, however, are obtained for other galaxies. These results involve a) calculating convincing models for a sample of 25 fairly well observed spirals (Roberts et al. 1975) and b) locating the compression zones on the inner edges of the spiral arms.

scholarly journals Interpretation of Observations of Spiral Structure in Terms of the Density Wave Theory

1974 ◽  
Vol 58 ◽  
pp. 399-412 ◽  
Author(s):  
Per Olof Lindblad
Keyword(s):  
Spiral Structure ◽  
Density Wave ◽  
Wave Theory ◽  
Density Waves ◽  
Density Wave Theory

A review is given of recent theoretical and observational work on the density wave theory of spiral structure. Emphasis is put on the kinematic picture, and the question whether modern observations reveal the existence of density waves is discussed.

scholarly journals TESTING DENSITY WAVE THEORY WITH RESOLVED STELLAR POPULATIONS AROUND SPIRAL ARMS IN M81

2015 ◽  
Vol 810 (1) ◽  
pp. 9 ◽  
Author(s):  
Yumi Choi ◽  
Julianne J. Dalcanton ◽  
Benjamin F. Williams ◽  
Daniel R. Weisz ◽  
Evan D. Skillman ◽  
...  
Keyword(s):  
Density Wave ◽  
Wave Theory ◽  
Stellar Populations ◽  
Spiral Arms ◽  
Density Wave Theory

Density wave theory and the classification of spiral galaxies

1975 ◽  
Vol 196 ◽  
pp. 381 ◽  
Author(s):  
W. W., Jr. Roberts ◽  
M. S. Roberts ◽  
F. H. Shu
Keyword(s):  
Spiral Galaxies ◽  
Density Wave ◽  
Wave Theory ◽  
Density Wave Theory

scholarly journals C. Spiral Structure

1985 ◽  
Vol 19 (1) ◽  
pp. 425-427
Keyword(s):  
Spiral Structure ◽  
Density Wave ◽  
Wave Theory ◽  
Density Waves ◽  
External Perturbations ◽  
Gravitational Theories ◽  
Recent Developments ◽  
Star Formation In Galaxies ◽  
Spiral Structures ◽  
Density Wave Theory

The spiral structure of galaxies is probably related to density waves, primarily governed by gravitational forces. Density waves may result from an inherent instability of galaxies against spiral perturbations as conceived in the conventional density-wave theory or may be forced by other internal or external perturbations of the gravitational field, such as neighbouring galaxies or oval distortions and bars in the inner regions of the galaxies. Reviews of recent developments on the various aspects of gravitational theories of spiral structure have been given by Ambastha and Varma (30.151.029), Athanassoula (33.151.051, 1984), Contopoulos (32.151.021, 34.151.103), Donner (30.151.085), Hunter (34.151.053), James and Wilkinson (29.151.023), Kalnajs (33.151.024), Kormendy (32.151.049), Lin (32.151.040, 33.151.025, 33.151.071), Lin and Bertin (30.151.068, 1984), Lin and Roberts (30.151.045), Martinet (30.151.043), McElroy (34.157.160), Norman (33. 157.088), Pasha and Tsitsin (34.151.042), Sorensen (29.151.024), Thonnard (31.158. 357), and Toomre (30.151.021). Seiden and Gerola (31.151.084) reviewed the theory of formation of spiral structures by stochastic self-propagating star formation in galaxies.

Nebula Tides and Gap Formation

1984 ◽  
Vol 5 (4) ◽  
pp. 461-464
Author(s):  
K. Hourigan ◽  
M. P. Schwarz
Keyword(s):  
Angular Momentum ◽  
Drift Rate ◽  
Density Wave ◽  
Wave Theory ◽  
Aggregation Process ◽  
Density Waves ◽  
Gap Formation ◽  
Orbital Drift ◽  
Radial Orbital ◽  
Density Wave Theory

An intriguing problem in cosmogony concerns the ability of a planetoid embedded in a nebula disc to clear a gap around its orbit. The application of density wave theory to this problem has demonstrated that a significant exchange of angular momentum can take place between a planetoid and a disc (Goldreich and Tremaine 1980). The torque exerted by the disc on the planetoid can result in orbital drifting of the latter, which may play an important role in the aggregation process (Hourigan and Ward 1983). In fact, in the absence of significant deformation of the nebula, the radial orbital drift rate of a planetoid increases with planetoid mass. In this case, it would be expected that only one or two planetoids would sweep out the nebula, a situation not compatible with present observations. The orbital drift resulting from the generation of density waves therefore requires a limiting mechanism.

scholarly journals The evolution of pitch angles of spiral arms

2019 ◽  
Vol 490 (1) ◽  
pp. 1470-1473 ◽  
Author(s):  
J E Pringle ◽  
C L Dobbs
Keyword(s):  
Pitch Angle ◽  
Spiral Galaxies ◽  
Spiral Structure ◽  
Density Wave ◽  
Wave Theory ◽  
Spiral Arms ◽  
First Approximation ◽  
Density Wave Theory ◽  
Self Gravity ◽  
Random Times

ABSTRACTIn spiral galaxies, the pitch angle, α, of the spiral arms is often proposed as a discriminator between theories for the formation of the spiral structure. In Lin–Shu density wave theory, α stays constant in time, being simply a property of the underlying galaxy. In other theories (e.g. tidal interaction, and self-gravity), it is expected that the arms wind up in time, so that to a first approximation $\cot \alpha \propto t$. For these theories, it would be expected that a sample of galaxies observed at random times should show a uniform distribution of $\cot \alpha$. We show that a recent set of measurements of spiral pitch angles (Yu & Ho) is broadly consistent with this expectation.

scholarly journals Determining the co-rotation radii of spiral galaxies using spiral arm pitch angle measurements at multiple wavelengths

2020 ◽  
Vol 496 (2) ◽  
pp. 1610-1619
Author(s):  
Shameer Abdeen ◽  
Daniel Kennefick ◽  
Julia Kennefick ◽  
Ryan Miller ◽  
Douglas W Shields ◽  
...  
Keyword(s):  
Pitch Angle ◽  
Spiral Galaxies ◽  
Density Wave ◽  
Wave Theory ◽  
Time Lapse ◽  
Spiral Arms ◽  
Infrared Wavelength ◽  
Angle Measurements ◽  
Density Wave Theory ◽  
Spiral Arm

ABSTRACT The spiral arms spanning disc galaxies are believed to be created by density waves that propagate through galactic discs. We present a novel method of finding the co-rotation radius where the spiral arm pattern speed matches the velocities of the stars within the disc. Our method uses an image-overlay technique, which involves tracing the arms of spiral galaxies on images observed in different wavelengths. Density wave theory predicts that spiral arms observed from different wavelengths show a phase crossing at the co-rotation radius. For the purpose of this study, 20 nearby galaxies were analysed in four different wavelengths with pitch angle measurements performed by two independent methods. We used optical wavelength images (B band 440 nm), two infrared wavelength images provided by Spitzer (3.6 and 8 μm) and ultraviolet images from GALEX (1350, 1750 Å). The results were compared and verified with other records found in the literature. We then found rotation curve data for six of our galaxies and used our co-rotation radii estimates to measure the time that would elapse between star formation and moving to their observed positions in the B-band spirals. The average time lapse for this motion was found to be ∼50 Myr. The success of this new method of finding the co-rotation radius confirms density wave theory in a very direct way.

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