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		| Paper: | 
		Isolating Red Giants in M31's Outer Spheroid: The Metallicity Gradient | 
	 
	
		| Volume: | 
		92, Formation of the Galactic Halo. . . . Inside and Out | 
	 
	
		| Page: | 
		540 | 
	 
	
		| Authors: | 
		Reitzel, David B.; Guhathakurta, Puragra; Gould, Andrew | 
	 
	
	
		| Abstract: | 
		The aim of our project is to measure the metallicity gradient in the spheroid of the Andromeda galaxy (M31). Deep KPNO 4-m UBRI images of a 15'times15 ' field in the outer spheroid of M31 are being used to isolate a sample of red giant branch (RGB) stars. These stars are distinguished from the more numerous distant field galaxies on the basis of broadband colors and image morphology. This technique yields a sample of candidate RGBs in M31's spheroid, located about 20kpc from its center (in projection). The shape of the M31 RGB is compared to those of Galactic globular clusters spanning a wide range of (known) metallicities. | 
	 
	
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