scholarly journals Amplitude of Spiral Arms and Dark Matter

2004 ◽  
Vol 220 ◽  
pp. 313-314
Author(s):  
P. Grosbøl
Keyword(s):  
Dark Matter ◽  
Spiral Galaxies ◽  
Spiral Structure ◽  
Dynamic Effects ◽  
Spiral Arms ◽  
Linear Dynamic ◽  
Total Potential ◽  
Force Perturbation ◽  
Barred Spiral Galaxies ◽  
Armed Spiral

Relative amplitudes and pitch angles for the main two-armed spiral structure in a sample of 54 non-barred spiral galaxies were estimated from K band photometry. A lack of strong, tight patterns was observed which may be caused by non-linear dynamic effects. Assuming that the upper envelope corresponds to a relative radial forcing of ⋐5%, one can estimate the perturbation of the total potential. This suggests that a maximum disk solution is adequate to account for the force perturbation and that no additional dark matter is required.

scholarly journals Outer spiral structure in disk galaxies

2016 ◽  
Vol 11 (S321) ◽  
pp. 123-123
Author(s):  
P.A. Patsis
Keyword(s):  
Periodic Orbits ◽  
Spiral Galaxies ◽  
Spiral Structure ◽  
Disk Galaxies ◽  
Spiral Arms ◽  
Chaotic Orbits ◽  
Grand Design ◽  
Pattern Speed ◽  
Spiral Structures ◽  
Barred Spiral Galaxies

AbstractIn several grand design barred-spiral galaxies it is observed a second, fainter, outer set of spiral arms. Typical examples of objects of this morphology can be considered NGC 1566 and NGC 5248. I suggest that such an overall structure can be the result of two dynamical mechanisms acting in the disc. The bar and both spiral systems rotate with the same pattern speed. The inner spiral is reinforced by regular orbits trapped around the stable, elliptical, periodic orbits of the central family, while the outer system of spiral arms is supported by chaotic orbits. Chaotic orbits are also responsible for a rhomboidal area surrounding the inner barred-spiral region. In general there is a discontinuity between the two spiral structures at the corotation region.

scholarly journals An HI Study of Two Barred Spiral Galaxies

1996 ◽  
Vol 157 ◽  
pp. 498-500
Author(s):  
E. M. Moore ◽  
S. T. Gottesman
Keyword(s):  
Spiral Galaxies ◽  
Spiral Structure ◽  
Hii Regions ◽  
Type Systems ◽  
Early Type ◽  
Late Type ◽  
Spiral Arms ◽  
Barred Spiral Galaxies ◽  
Pattern Speeds

We have made HI observations of an early type, NGC 1398 (SBab(r)I), and a late type barred system, NGC 3319 (SBc(s)II.4). NGC 1398 is a beautifully symmetric galaxy with a bright stellar bulge, bar and inner ring and tightly wound spiral arms (also classified as an R1 double outer pseudoring). In HI the spiral structure is strong but the center shows a sharp depletion. In contrast, NGC 3319 has an asymmetric appearance and irregular spiral structure. It is rich in its central HI with a gas bar and spiral arms, both of which are highlighted by prominent HII regions. We attempt to determine the pattern speeds of the galaxies and to explore the differences between early and late type systems.

scholarly journals The Dark Matter Content of Barred Spiral Galaxies

2004 ◽  
Vol 220 ◽  
pp. 277-278
Author(s):  
Glen Petitpas ◽  
Mousumi Das ◽  
Peter Teuben ◽  
Stuart Vogel
Keyword(s):  
Dark Matter ◽  
Spiral Galaxies ◽  
Velocity Fields ◽  
Matter Content ◽  
Two Dimensional ◽  
Disk Model ◽  
Barred Galaxies ◽  
Preliminary Results ◽  
Nearby Galaxies ◽  
Barred Spiral Galaxies

Two-dimensional velocity fields have been used to determine the dark matter properties of a sample of barred galaxies taken from the BIMA Survey of Nearby Galaxies (SONG). Preliminary results indicate that the maximal disk model is not appropriate in several galaxies in our sample, but higher resolution results will be needed to confirm this.

scholarly journals Barred spiral galaxies

1970 ◽  
Vol 38 ◽  
pp. 351-355
Author(s):  
K. C. Freeman
Keyword(s):  
Spiral Galaxies ◽  
Spiral Structure ◽  
Theoretical Work ◽  
Barred Spiral Galaxies

We point out some properties of barred spiral galaxies which are important for the theory of their formation and spiral structure, and describe some theoretical work on the dynamics of these systems.

STRUCTURES OUT OF CHAOS IN BARRED-SPIRAL GALAXIES

2012 ◽  
Vol 22 (09) ◽  
pp. 1230029 ◽  
Author(s):  
P. A. PATSIS
Keyword(s):  
Near Infrared ◽  
Spiral Galaxies ◽  
Morphological Features ◽  
Infrared Images ◽  
Chaotic Motions ◽  
Spiral Arms ◽  
Gravitational Fields ◽  
Pattern Speed ◽  
Barred Spiral Galaxies ◽  
Kinematical Data

We review the dynamical mechanisms we have found to support the morphological features in barred-spiral galaxies based on chaotic motions of stars in their gravitational fields. These morphological features are the spiral arms, that emerge out of the ends of the bar, but also shape the bar itself. The potentials used have been estimated directly from near-infrared images of barred-spiral galaxies. In this paper, we present the results from the study of the dynamics of the potentials of the galaxies NGC 4314, NGC 1300 and NGC 3359. The main unknown parameter in our models is the pattern speed of the system Ωp. By varying Ωp, we have investigated several cases trying to match the results of our modeling with available photometrical and kinematical data. We found realistic models with stars on spirals in chaotic motion, while their bars are built by stars usually on regular orbits. However, we also encountered cases, where a major part of trajectories of the stars even in the bar is chaotic as well. Finally, we examined the gas dynamics of barred-spiral systems, and found that the presence of gas reinforces the intensity of the "chaotic" spiral arms.

Circumnuclear Spiral Arms and Starburst Rings in Magnetized Barred Spiral Galaxies

2001 ◽  
Vol 553 (1) ◽  
pp. L35-L38 ◽  
Author(s):  
Yu-Qing Lou ◽  
Chi Yuan ◽  
Zuhui Fan ◽  
Stephane Leon
Keyword(s):  
Spiral Galaxies ◽  
Spiral Arms ◽  
Barred Spiral Galaxies

scholarly journals Theory of Spiral Structure

1971 ◽  
Vol 2 ◽  
pp. 88-121 ◽  
Author(s):  
C. C. Lin
Keyword(s):  
Theoretical Analysis ◽  
Observational Data ◽  
Spiral Galaxies ◽  
Spiral Structure ◽  
Interstellar Matter ◽  
Spiral Arms ◽  
The Subject ◽  
To Receive

It is an honor for me to continue the discussion of galactic spirals following Professor Bok, who has contributed to the subject for many years. My experience has been relatively short. My first encounter with the study of galactic spirals occurred in 1961, when I was invited by Professor Bengt Strömgren to attend a conference on interstellar matter at Princeton, N.J. There I first learned about the winding dilemma from Professor Jan Oort. After the conference, Professor Lodewijk Woltjer, who edited the Proceedings, visited me for about a month. Thus, I began slowly to learn about spiral galaxies and to work on the subject. It turned out to be an extremely rewarding experience, for the observational data were already ripe for theoretical analysis, and the hydromagnetic theory of spiral arms was clearly encountering great difficulties. Since I was not educated as an astronomer, I owe my gratitude to Professors Strömgren, Woltjer, and Kevin Prendergast, on whom I depended for correct astronomical facts as I started my work. Without their help, I would not be standing here today. Later on, I was to receive help from many other distinguished astronomers, including Professor Bok from whom you just heard. I am greatly impressed with the community of astronomers as a dedicated group of scientists.

scholarly journals A Circulation Hypothesis of Spiral Galaxies

1998 ◽  
Vol 188 ◽  
pp. 293-294
Author(s):  
Chen Linfei
Keyword(s):  
Spiral Galaxies ◽  
Spiral Structure ◽  
Galactic Center ◽  
Circulatory System ◽  
Spiral Arms ◽  
The Galaxy ◽  
Spiral Arm

A circulation hypothesis of spiral galaxies is proposed here to explain their spiral structure: the spiral arm material is going to the galactic center along a spiral orbit and then ejects from the galactic center in the form of two-way jets in opposite directions and finally, the ejected jets return to the galaxy in the form of spiral arms again, thereby forming a closed circulatory system.

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