AAS 205th Meeting, 9-13 January 2005
Session 169 Dwarf Galaxies Near and Far and Some Starbursts
Oral, Thursday, January 13, 2005, 2:00-3:30pm, Pacific Salon 1

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[169.03] Tidal Tails and Multiple Components: the not-so-simple dwarf spheroidals of the Local Group

A.W. McConnachie, M.J. Irwin (Institute of Astronomy, Cambridge, UK), R.A. Ibata (Observatoire de Strasbourg, France), A.M.N. Ferguson (M.P.A., Garching, Germany), G.F. Lewis (University of Sydney, Australia), N. Tanvir (University of Hertfordshire, U.K)

We have obtained imaging of all the dwarf spheroidal satellites of the Andromeda Galaxy, and analysed their morphology via resolved star counts. A startling variety in their structure is seen. In particular all but a few show strong evidence of tidal disruption. This is most spectacularly demonstrated by Andromeda I, whose isopleths show clear evidence of extended tidal tails. Even more surprising than this, however, is the structure of Andromeda II, where central star counts clearly require a two component stellar model to explain the data. Taken in conjunction with recent results on Galactic dwarf spheroidals, this suggests that dwarf spheroidal galaxies are not the simple dynamical systems that we have assumed. Implications for their derived properties, formation and subsequent evolution will be discussed.

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Bulletin of the American Astronomical Society, 36 5
© 2004. The American Astronomical Society.