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Title: Stellar Kinematics and Metallicities in the Leo I Dwarf Spheroidal Galaxy-Wide-Field Implications for Galactic Evolution
Authors: Koch, A.
Wilkinson, M. I.
Kleyna, J. T.
Gilmore, G. F.
Grebel, E. K.
Mackey, A. D.
Evans, N. W.
Wyse, R. F. G.
First Published: 1-Mar-2007
Publisher: American Astronomical Society, IOP Publishing
Citation: Astrophysical Journal, 2007, 657 (1), pp.241-261
Abstract: We present low-resolution spectroscopy of 120 red giants in the Galactic satellite dwarf spheroidal (dSph) Leo I, obtained with GeminiN GMOS and Keck DEIMOS. We find stars with velocities consistent with membership of Leo I out to 1.3 King tidal radii. By measuring accurate radial velocities with a median measurement error of 4.6 km s-1, we find a mean systemic velocity of 284.2 km s-1 with a global velocity dispersion of 9.9 km s-1. The dispersion profile is consistent with being flat out to the last data point. We show that a marginally significant rise in the radial dispersion profile at a radius of 3' is not associated with any real localized kinematical substructure. Given its large distance from the Galaxy, tides are not likely to have affected the velocity dispersion, a statement we support from a quantitative kinematical analysis, as we observationally reject the occurrence of a significant apparent rotational signal or an asymmetric velocity distribution. Mass determinations adopting both isotropic stellar velocity dispersions and more general models yield an M/L of 24, which is consistent with the presence of a significant dark halo with a mass of about 3 × 107 M☉, in which the luminous component is embedded. This suggests that Leo I exhibits dark matter properties similar to those of other dSphs in the Local Group. Our data allowed us also to determine metallicities for 58 of the targets. We find a mildly metal-poor mean of -1.31 dex and a full spread covering 1 dex. In contrast to the majority of dSphs, Leo I appears to show no radial gradient in its metallicities, which points to a negligible role of external influences in this galaxy's evolution.
DOI Link: 10.1086/510879
ISSN: 0004-637X
Type: Article
Rights: Archived with reference to SHERPA/RoMEO and publisher website. Copyright 2007. The American Astronomical Society. All rights reserved.
Appears in Collections:Published Articles, Dept. of Physics and Astronomy

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