NOAO >   Observing Info >   Approved Programs >   2002A-0300

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Proposal Information for 2002A-0300


PI: Michael H. Siegel, Space Telescope Science Institute, msiegel@stsci.edu
Address: 3700 San Martin Drive, Baltimore, MD 21218, US

CoI: Steven R. Majewski, University of Virginia

Title: The Proper Motion of the Leo II dSph Galaxy

Abstract: We propose to obtain spectra of almost three dozen QSO candidates we have identified around the Leo II dSph galaxy in order to define a sample of positively identified QSOs that can be used to establish an astrometric inertial reference frame. Confirming the nature of these compact objects is critical to setting the absolute reference frame for our \it existing catalogue of extremely accurate (\sigma_(mu) ~ 0.15 mas yr^-1), \it relative proper motions for objects in the Leo II field. Refining the absolute proper motion of Leo II will allow determination of the orbit for one of the most distant known Milky Way satellites. Because Leo II is at a distance of 215 kpc, determining its orbit can provide an important constraint on the mass of the Milky Way. It will also provide insight into the dynamical history of Leo II - in particular whether it is the tidal debris of a destroyed Fornax-Leo- Sculptor progenitor galaxy, as has been postulated by Lynden-Bell (1982).


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NOAO >   Observing Info >   Approved Programs >   2002A-0300

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