NOAO >   Observing Info >   Approved Programs >   2006B-0423

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Proposal Information for 2006B-0423


PI: Steven R. Majewski, University of Virginia, srm4n@virginia.edu
Address: Department of Astronomy, P.O. Box 400325, Charlottesville, VA 22904-4325, USA

CoI: Richard J. Patterson, University of Virginia
CoI: Puragra Guhathakurta, UC-Santa Cruz
CoI: R. Michael Rich, UC-Los Angeles
CoI: Jason Kalirai, UC-Santa Cruz

Title: Exploring the Newly Discovered Halo Of M31

Abstract: Understanding the formation of galaxies and their structural components is a goal of modern cosmology. Cold dark matter models make specific predictions about the shape, extent and smoothness of halos, but few halos outside the Milky Way's (MW) have been explored for even the most basic, global properties; even the MW halo presents some difficulties for study from within. But M31 offers a global external perspective and yet is close enough for us to resolve individual stars. Recently, using Mayall 4-m + Mosaic photometry in the Washington M, T_2 + DDO51 filters and follow-up spectroscopy of identified M31 giant candidates, we made the first direct and unambiguous detection of the M31 halo, and traced its projected r^-2 density profile to 150 kpc along the minor axis. We propose to expand on this discovery by (1) continuing this first systematic photometric and spectroscopic study of the extent, shape, smoothness, and chemodynamics of the newly found M31 halo to even larger radii, (2) checking whether there is an M33 halo and clarifying whether it overlaps the M31 halo, (3) searching for new streams/substructure in the outer halo, and (4) use our very sensitive techniques to survey the more challenging and less studied northeast side of M31. We will obtain the first measure of the dynamics, kinematical substructure and metallicity gradient of the M31 halo to (mu)_V$>$35 mag arcsec^-2, and thereby provide direct constraints on hierarchical formation models.


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