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		| Paper: | 
		The Stars and Gas in Outer Parts of Galaxy Disks: Extended or Truncated, Flat or Warped? | 
	 
	
		| Volume: | 
		396, Formation and Evolution of Galaxy Disks | 
	 
	
		| Page: | 
		173 | 
	 
	
		| Authors: | 
		van der Kruit, P.C. | 
	 
	
	
		| Abstract: | 
		I review observations of truncations of stellar disks and models for their origin, compare observations of truncations in moderately inclined galaxies to those in edge-on systems and discuss the relation between truncations and H I-warps and their systematics and origin. Truncations are a common feature in edge-on stellar disks, but the relation of truncations in face-on to those in edge-on galaxies needs further clarification. The origin of truncations is most likely related to a maximum in the specific angular momentum in the material that formed the stellar disks, but this model does probably require some redistribution of angular momentum. H I-warps start just beyond the truncation radius and disks and warps appear distinct components. This suggests that inner disks form initially and settle as rigid, very flat structures, while H I-warps result from later infall of gas with a different orientation of the angular momentum. | 
	 
	
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