AAS 200th meeting, Albuquerque, NM, June 2002
Session 46. Astrophysics in the Local Group
Display, Tuesday, June 4, 2002, 10:00am-6:30pm, SW Exhibit Hall

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[46.01] Evidence for Substructure in the Halo of M31

A. M. N. Ferguson (Kapteyn Institute, Groningen), M. J. Irwin (Institute of Astronomy, Cambridge), R. A. Ibata (Observatoire de Strasbourg), G. F. Lewis (Anglo-Australian Observatory), N. R. Tanvir (University of Hertfordshire)

We report results from our ongoing survey of the outer disk and halo of M31 with the Wide-Field Camera on the INT 2.5m. To date, we have mapped a region of ~25 square degrees centered on M31, extending out to a major axis radius of ~55 kpc. The contiguous nature of our survey allows the first uninterrupted study of the density and colour distribution of individual red giant branch stars. We find evidence for both spatial density and metallicity variations, which are often, but not always, correlated. In addition to the previously-reported giant stellar stream (Ibata et al 2001), our data reveal the presence of significant stellar overdensities at large radii close to the south-western major axis, in the proximity of the luminous globular cluster G1, and near the north-eastern major axis, coinciding with and extending beyond the previously-known `northern spur'. Additional lower-level overdensities are seen at various locations. We discuss the possible origin of these large-scale inhomogeneities and the implications for constraining the galaxy assembly process.

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Bulletin of the American Astronomical Society, 34
© 2002. The American Astronomical Soceity.