On the Interaction of Spiral Density Waves with Stars near the Inner Lindblad Resonance in Galactic Disks

2018 ◽  
Vol 44 (11) ◽  
pp. 664-675
Author(s):  
E. V. Polyachenko ◽  
I. G. Shukhman
Keyword(s):  
Density Waves ◽  
Galactic Disks ◽  
Spiral Density Waves ◽  
Lindblad Resonance ◽  
Inner Lindblad Resonance

scholarly journals Density waves and the viscous overstability in Saturn’s rings

2019 ◽  
Vol 623 ◽  
pp. A121 ◽  
Author(s):  
M. Lehmann ◽  
J. Schmidt ◽  
H. Salo
Keyword(s):  
Large Scale ◽  
Density Wave ◽  
Relative Magnitude ◽  
Density Waves ◽  
Scale Free ◽  
Short Scale ◽  
Spiral Density Waves ◽  
Saturn’S Rings ◽  
Saturn's Rings ◽  
Lindblad Resonance

This paper considers resonantly forced spiral density waves in a dense planetary ring that is close to the threshold for viscous overstability. We solved numerically the hydrodynamical equations for a dense thin disk in the vicinity of an inner Lindblad resonance with a perturbing satellite. Our numerical scheme is one-dimensional so that the spiral shape of a density wave is taken into account through a suitable approximation of the advective terms arising from the fluid orbital motion. This paper is a first attempt to model the co-existence of resonantly forced density waves and short-scale free overstable wavetrains as observed in Saturn’s rings, by conducting large-scale hydrodynamical integrations. These integrations reveal that the two wave types undergo complex interactions, not taken into account in existing models for the damping of density waves. In particular we found that, depending on the relative magnitude of both wave types, the presence of viscous overstability can lead to the damping of an unstable density wave and vice versa. The damping of the short-scale viscous overstability by a density wave was investigated further by employing a simplified model of an axisymmetric ring perturbed by a nearby Lindblad resonance. A linear hydrodynamic stability analysis as well as local N-body simulations of this model system were performed and support the results of our large-scale hydrodynamical integrations.

scholarly journals Spiral patterns beyond the optical radius: numerical simulations and synthetic HI observations

2016 ◽  
Vol 11 (S321) ◽  
pp. 81-83
Author(s):  
Sergey Khoperskov ◽  
Giuseppe Bertin
Keyword(s):  
Large Scale ◽  
Spiral Structure ◽  
Stellar Disk ◽  
Small Scale ◽  
Density Waves ◽  
Spiral Density Waves ◽  
Hydrodynamical Simulations ◽  
Lindblad Resonance ◽  
Regular Patterns ◽  
Optical Radius

AbstractThe outer parts of many galaxy disks exhibit extended spiral arms far beyond the optical radius. To understand the nature and the origin of such outer spiral structure, we investigate the propagation in the outer gaseous regions of large-scale spiral density waves excited in the bright optical disk. By means of 3D hydrodynamical simulations, we show that spiral density waves, penetrating in the gas through the outer Lindblad resonance, can indeed give rise to relatively regular patterns outside the bright optical stellar disk. The amplitude of spiral structure increases rapidly with radius. Beyond the optical radius, spirals become nonlinear and develop small-scale features related to shear-induced instabilities. We also construct the synthetic 21-cm data cubes extracted from simulated gaseous disks. Our synthetic HI observations point to the existence of specific kinematical features related to the presence of spiral pattern perturbations that should be found in deep HI observations.

scholarly journals Star Formation in Normal Irregular Galaxies

1987 ◽  
Vol 115 ◽  
pp. 611-612
Author(s):  
Deidre A. Hunter
Keyword(s):  
Star Formation ◽  
Large Range ◽  
Density Waves ◽  
Regulatory Processes ◽  
Spiral Density Waves ◽  
Global Properties ◽  
Level Of Activity ◽  
Star Formation Activity ◽  
Irregular Galaxies

Normal, non-interacting irregular galaxies can be quite successful at forming stars. Therefore, spiral density waves are not necessary to a vigorous production of stars. Nevertheless, there is a large range in star-formation rates among irregular galaxies. Irregulars with common characteristics can have different overall levels of star-formation activity, so that the level of activity does not seem to be simple related to observable global properties of galaxian systems. The constant star formation rates of most normal irregulars also imply the existence of regulatory processes.

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 A Nuclear Ring in the Sa(r!) Galaxy NGC 7742

1996 ◽  
Vol 157 ◽  
pp. 83-85 ◽  
Author(s):  
K. Wakamatsu ◽  
M. Hamabe ◽  
M. T. Nishida ◽  
A. Tomita
Keyword(s):  
Elliptical Galaxy ◽  
Formation Mechanisms ◽  
Main Body ◽  
Circular Symmetry ◽  
Barred Galaxies ◽  
Exclamation Mark ◽  
The Galaxy ◽  
Nuclear Ring ◽  
Lindblad Resonance ◽  
Inner Lindblad Resonance

NGC 7742 is well known for its prominent blue nuclear ring around an EO-like core, and so appears as a Hoag-type galaxy, an elliptical galaxy with an outer ring (Schweizer et al. 1987). The galaxy is classified as Sa(r!) in the Revised Shapley-Ames Catalog (Sandage and Tammann 1987) with an exclamation mark to emphasize the prominence of the ring. Its photographs are published in Laustsen et al. (1987), Wray (1988), and Sandage & Bedke (1994).The ring has a diameter of 19″ = 1.6 kpc at a distance of 17.1 Mpc (Buta & Crocker 1993), and so should be a nuclear ring of the galaxy. Nuclear rings and pseudorings are often detected in strongly barred (SB) galaxies, and interpreted to be linked to the inner Lindblad resonance (Buta & Crocker 1993). These nuclear features are, however, also found in some weakly-barred (SAB) and non-barred (SA) galaxies. NGC 7742 is a galaxy of the highest circular symmetry in its core, ring, and main body, and so the best object for a detailed study of formation mechanisms of nuclear rings in non-barred galaxies.

scholarly journals On the use of the WKBJ density wave theory at the Inner Lindblad Resonance region of our galaxy

1979 ◽  
Vol 84 ◽  
pp. 191-192
Author(s):  
E. Athanassoula
Keyword(s):  
Density Wave ◽  
Wave Theory ◽  
Resonance Region ◽  
Density Wave Theory ◽  
Lindblad Resonance ◽  
Inner Lindblad Resonance

I have tested the reliability of certain approximations involved in the asymptotic WKBJ density wave description of the inner Lindblad resonance (=ILR) of our galaxy.

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