AAS 207th Meeting, 8-12 January 2006
Session 123 RAVE
Poster, Wednesday, 9:20am-6:30pm, January 11, 2006, Exhibit Hall

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[123.09] Further Evidence for a Merger Origin for the Thick Disk: Galactic Stars Along Lines-of-sight to Dwarf Spheroidal Galaxies

R.F.G. Wyse (JHU), G. Gilmore (IoA, Cambridge), J.E. Norris (RSAA, ANU), M.I. Wilkinson (IoA, Cambridge), J.T. Kleyna (IfA, Hawaii), A. Koch (Basel), N.W. Evans (IoA, Cambridge), E.K. Grebel (Basel)

The history of the Milky Way Galaxy is written in the properties of its stellar populations. Here we analyse stars observed as part of surveys of local dwarf spheroidal galaxies, but which from their kinematics are highly probable to be non-members. The selection function -- designed to target metal-poor giants in the dwarf galaxies, at distances of around 100 kpc -- includes F-M dwarfs in the Milky Way, at distances of up to several kpc. The stars whose motions are analysed here lie close to the cardinal directions of Galactic longitude \ell=270circ and \ell=90circ, where the radial velocity is sensitive to the orbital rotational velocity, V\phi. We demonstrate that the faint F/G stars contain a significant population with V\phi ~100 km/s, which does not match either the canonical thick disk or the stellar halo. We argue that this apparently pervasive population has the expected properties of `satellite debris' in the thick-disk/halo interface, which we interpret as remnants of the merger that heated a pre-existing thin disk to form the thick disk.

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