NOAO >   Observing Info >   Approved Programs >   2003A-0383

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Proposal Information for 2003A-0383


PI: Steven R. Majewski, University of Virginia, srm4n@virginia.edu
Address: Astronomy Department, P.O. Box 3818, Charlottesville, VA 22936-0818, USA

CoI: Michael F. Skrutskie, University of Virginia
CoI: Kathryn V. Johnston, Wesleyan University
CoI: Jeffrey D. Crane, University of Virginia
CoI: Richard J. Patterson, University of Virginia
CoI: William E. Kunkel, Las Campanas Observatory
CoI: Martin Weinberg, University of Massachusetts

Title: Spectroscopy of Stars in the First All-Sky View of the Sagittarius Dwarf+Tail System

Abstract: \vskip -0.2in We have assembled the first all-sky view of the Sagittarius (Sgr) dwarf galaxy and its tidal tail system by identifying constituent M giant stars with 2MASS. This infrared photometry yields a clean image of the Sgr core, which follows a ``King + power law break" profile that looks identical to break profiles previously observed (and debated) in other Galactic dSphs. Sgr is the most accessible member of this family of dSphs, and one where the break is from \it certain tidal disruption. We seek 1 km/s radial velocities (RVs) of Sgr stars within the King radius to determine whether and how disruption affects the velocity profiles of dSphs, for direct comparison to dSph dark matter and disruption models as well as velocity data in these other dSphs. We also find prominent leading and trailing tidal arms wrapped completely around the Galaxy. Several km/s RVs for stars in these arms will help to determine their true length (therefore the duration of the Sgr-Milky Way interaction), discriminate whether/where the leading arm passes through the Galactic plane on this side of the Galactic center, define the Sgr orbit with high precision and constrain the form of the Galactic potential, and yield insights into how an apparently fluffy Sgr could have survived for a Hubble time.


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