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D. Harbeck, E.K. Grebel (MPIfA), W. Brandner (ESO), A. Dolphin (NOAO), D. Geisler (U. de Concepcion, Chile), Jon Holtzman (NMSU), D. Hurley-Keller (CWRU), M. Mateo (U. Michigan), A. Sarajedini (U. Florida)
For several Local Group (LG) dwarf spheroidal galaxies (dSphs) radial gradients in the horizontal branch morphology were reported. We present a systematic and homogeneous analysis of population gradients of Helium burning stars for the LG dSphs Carina, Sculptor, Sextans, Tucana, Andromeda I-III, V, and VI. Additionally we analyze the transition type galaxy Phoenix. For all of the Milky Way companions studied here we found significant population gradients.The same is true for the remote dSph Tucana located at the outskirts of the LG. In all of these cases, the red horizontal branch (HB) stars are more centrally concentrated than the blue ones. Among the M\,31 dSph companions only the Andromeda I, V, and VI galaxies show obvious gradients, while the morphologies of And III and V show only weak or no HB variation with galactocentric radius. The HB morphology gradients do not appear to be correlated with the present-day distance of the dSphs to the nearest massive spiral galaxy or absolute luminosity of the dSphs.
The author(s) of this abstract have provided an email address for comments about the abstract: dharbeck@mpia.de