NOAO >   Observing Info >   Approved Programs >   2009B-0550

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Proposal Information for 2009B-0550


PI: Rachael L. Beaton, U. Virginia, rlb9n@virginia.edu
Address: Astronomy Department, PO Box 400325, Charlottesville, VA 22904, USA

CoI: Steven R. Majewski, U. Virginia
CoI: Richard J. Patterson, U. Virginia
CoI: Puragra Guhathakurta, U.C. Santa Cruz
CoI: James S. Bullock, U.C. Irvine
CoI: Jason Kalirai, Space Telescope Science Institute
CoI: Karoline Gilbert, U. Washington

Title: Exploring the Merger History of M31

Abstract: In CDM simulations, galaxies form hierarchically through merger events. Due to sparse stellar density and long dynamical timescales, stellar halos should be particularly suitable for studying this history, with all stages of minor merging preserved in luminous structures; this includes very early mergers now making up the inner spheroids, intermediate-aged accretions in the form of coherent stellar streams, recent accretions seen as tidally disrupting dSphs, and future accretions represented by still-intact satellites. Clearly, the study of nearby, \it resolved massive galaxy halos, like those of the Milky Way (MW) and M31, are vital to providing observational feedback for testing cosmological simulations with unparalleled detail. We propose to use Mosaic + Keck/Deimos to study all stages of merging history in the M31 stellar halo by (1) exploring newly discovered M31 satellites (e.g. Irwin et al. 2008), most expected to be future mergers, but including at least some present mergers, like the tidally disrupted AndXIX dSph (McConnachie et al. 2008); (2) investigating the relatively recent merger seen as the Great Southern Stream (Ibata et al. 2001, Gilbert et al. 2007, Fardal et al. 2008) and associated substructures, (3) continuing to characterize older mergers, seen as substructure in the outer M31 (and M33) halo, and (4) further defining the character of the inner M31 spheroid.


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