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P. Guhathakurta, P.I. Choi (UCSC), D.B. Reitzel (UC Irvine)
It has long been suspected that the stellar disk of M31 harbors a substantial warp in its outer parts. Recent CCD mosaic imaging and surface photometry in the B and I bands appear to confirm the presence of low surface brightness features at both ends of the major axis of the galaxy. In an unrelated Keck spectroscopic survey of individual red giant stars in a field located on the minor axis of M31 at a projected distance of 19~kpc, we find a handful of exceptionally metal-rich stars whose kinematics are consistent with their being members of M31's disk, rather than its spheroid. This suggests that M31's disk is unusually large (R~80~kpc!) and/or warped. If confirmed, this would represent the most extreme case of a warped stellar disk ever observed in a spiral galaxy.