Exploring halo substructure with giant stars: The velocity dispersion profiles of the ursa minor and Draco dwarf spheroidal galaxies at large angular separations

Munoz, RR; Frinchaboy, PM; Majewski, SR; Kuhn, JR; Chou, MY; Palma, C; Sohn, ST; Patterson, RJ; Siegel, MH

Abstract

We analyze velocity dispersion profiles for the Draco and Ursa Minor (UMi) dwarf spheroidal (dSph) galaxies based on published and new Keck HIRES spectra for stars in the outer UMi field. Washington + DDO51 filter photometric catalogs provide additional leverage on membership of individual stars and, beyond 0.5 King limiting radii (r(lim)), identify bona fide dSph members up to 4.5 times more efficiently than simple color-magnitude diagram selections. Previously reported "cold populations" at r(lim) are not obvious in the data and appear only with particular binning; more or less constant and platykurtic dispersion profiles are characteristic of these dSphs to large radii. We report the discovery of UMi stars to at least 2.7r(lim) (i.e., 210' or 4 kpc). Even with conservative assumptions, a UMi mass of M > 4.9 x 10(8) M-circle dot is required to bind these stars, implying an unlikely global mass-to-light ratio M/L > 900 (M/L)(circle dot). We conclude that we have found stars tidally stripped from UMi.

Más información

Título según WOS: ID WOS:000232365700010 Not found in local WOS DB
Título de la Revista: ASTROPHYSICAL JOURNAL
Volumen: 631
Número: 2
Editorial: IOP PUBLISHING LTD
Fecha de publicación: 2005
Página de inicio: L137
Página final: L141
DOI:

10.1086/497396

Notas: ISI