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Secular Evolution and the Morphological Transformation of Cluster and Field Galaxies

Published online by Cambridge University Press:  01 August 2006

Xiaolei Zhang  and
Ronald J. Buta
Xiaolei Zhang
Affiliation:
Remote Sensing Division, U.S. Naval Research Lab, 4555 Overlook Ave. SW, Washington, DC 20375, USA email: [email protected]
Ronald J. Buta
Affiliation:
Department Physics and Astronomy, University of Alabama, 514 University Blvd E, Box 870324, Tuscaloosa, AL 35401, USA email: [email protected]
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Abstract

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Deep surveys conducted during the past decades have shown that galaxies in the distant universe are generally of more irregular shapes, and are disky in appearance and in their star formation rate, compared to galaxies in similar environments in the nearby universe. Given that the merger rate between z= 2 and the local universe is far from adequate to account for this observed morphological transformation rate, an internal mechanism for the morphological transformation of galaxies is to be sought, whose operation can be further aided by environmental factors. The secular evolution mechanism, especially with the discovery of a collisionless dissipation mechanism for stars within the secular evolution paradigm, has provided just such a framework for understanding the morphological evolution of galaxies across the Hubble time. In this paper we will summarize the past theoretical results on the dynamical mechanisms for secular evolution, and highlight new results in the analysis of the observational data, which confirmed that density waves in physical galaxies possess the kind of characteristics which could produce theáobserved rates of morphological transformation for both cluster and field galaxies.

Keywords

galaxy structuregalaxy dynamicsgalaxy evolution
Type
Contributed Papers
Information
Proceedings of the International Astronomical Union , Volume 2 , Symposium S235: Galaxy Evolution Across the Hubble Time , August 2006 , pp. 184 - 186
Copyright
Copyright © International Astronomical Union 2007

References

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