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Multiple Gas Rings in SA Galaxies

Published online by Cambridge University Press:  12 April 2016

J. Palouš  and
B. Jungwiert
J. Palouš
Affiliation:
Astronomical Institute, Academy of Sciences of the Czech Republic, Boční II, 141 31 Prague 4, Czech Republic
B. Jungwiert
Affiliation:
Astronomical Institute, Academy of Sciences of the Czech Republic, Boční II, 141 31 Prague 4, Czech Republic

Extract

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Rings are frequently observed in barred galaxies (e.g. Buta & Crocker 1993). Their origin is attributed to gas accumulation near resonances, which is due to a combination of the gravitational torques of a bar component acting on inelastically colliding clouds: outer rings are presumably associated with the Outer Lindblad Resonance (OLR), inner rings with the 4/1 resonance, and nuclear rings with the Inner Lindblad Resonance (ILR).

However, multiple rings are also observed in normal non-barred, or not obviously barred galaxies (e.g. NGC 7217, Verdes-Montenegro et al. 1995) so that we may ask what is the mechanism of their formation. We argue in this contribution that even a very weak bar or a triaxial distortion in the galaxy center, which would hardly be identified from observations, leads to long-lasting ring-like distributions of gaseous clouds. The formation time-scales of rings associated with different resonances are similar in our model so that all types of rings can coexist in galaxies with a high degree of axial symmetry in their central parts, such as SA galaxies.

Type
Posters of Part V and Part VI
Information
International Astronomical Union Colloquium , Volume 157: Barred Galaxies , 1996 , pp. 369 - 371
Copyright
Copyright © Astronomical Society of the Pacific 1996

References

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