The peculiar knotty and lumpy structures of many high

The peculiar knotty and lumpy structures of many high - The...

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The peculiar knotty and lumpy structures of many high-redshift galaxies has led to models for wholesale morphological evolution. This issue is still unresolved because many galaxies become less symmetric when observed in the emitted UV, and because cosmological surface-brightness dimming strongly favors the detection of galaxies with high-surface brightness regions of star formation. Work in the emitted optical range (observed near-IR) should make real progress here now that adaptive optics can deliver even better resolution than NICMOS, and will surely be a major product of NGST. Mergers certainly drive some present-day morphological evolution. Toomre in 1977 estimated a merger rate which is pretty close to later estimates like Keel and Wu (1995 AJ 110, 129) and Borne and Cheung (2000 DDA abstract 32.1101). The upshot is that bright galaxies suffer major mergers at a rate 0.3-0.4 per Hubble time, with most of this concentrated in systems that are part of bound pairs. Structures such as rings also indicate that galaxies evolve dynamically at different rates; models suggest that stars may be driven into a stable bulge+ring configuration, and that even disk
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The peculiar knotty and lumpy structures of many high - The...

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