NOAO >   Observing Info >   Approved Programs >   2007A-0559

Small NOAO Logo

Proposal Information for 2007A-0559


PI: Steven R. Majewski, University of Virginia, srm4n@virginia.edu
Address: Department of Astronomy, P. O. Box 3818, Charlottesville, VA 22903-0818, USA

CoI: Christine Drown, University of Virginia
CoI: Ricardo Munoz, University of Virginia
CoI: Richard J. Patterson, University of Virginia
CoI: Chris Palma, Penn State University
CoI: Michael Siegel, University of Texas

Title: Proof of Tidal Tails from the Ursa Minor dSph Galaxy?

Abstract: The Sgr dwarf galaxy + tidal tail system, now extensively explored by the 2MASS and SDSS databases, provides a clear example of a Milky Way satellite in tidal disruption. But is Sgr the exception or the \it paradigm of dSph galaxies? Interesting clues suggest the latter: Other dSph galaxies exhibit very extended surface brightness profiles and approximately \it flat velocity dispersion profiles, as does Sgr out into its tidal arms and as do N-body models of disrupting dSphs. However, our conclusions remain tentative without definitively observed tidal arms in the other dSphs, a problem that keeps alive the debate on whether the extended dSph populations are tidal debris or bound dSph halos. However, with Mosaic time awarded last year, we have extended the length along the major axis of the UMi dSph over which we have observed an apparent excess of UMi blue horizontal branch (BHB) candidates to ~7 deg or ~8 kpc. We now propose to (1) use the HET to obtain radial velocities of these BHB candidates in order to prove their association to UMi and look for the velocity gradient signature of a tidal tail, and (2) further map the UMi area with Mosaic, including more area toward the minor axis, to test for the azimuthal asymmetry expected for a tidal tail. (This project is the proposed UVa undergraduate Senior Thesis of Christine Drown).


National Optical Astronomy Observatory, 950 North Cherry Avenue, P.O. Box 26732, Tucson, Arizona 85726, Phone: (520) 318-8000, Fax: (520) 318-8360



NOAO >   Observing Info >   Approved Programs >   2007A-0559

noaoprop-help@noao.edu

Small NOAO Logo