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We present moderate resolution (~6 km/s) spectroscopy of 284 M giantcandidates selected from the Two Micron All Sky Survey photometry. Radialvelocities (RVs) are presented for stars mainly in the south, with a numberhaving positions consistent with association to the trailing tidal tail of theSagittarius (Sgr) dwarf galaxy. The latter show a clear RV trend with orbitallongitude, as expected from models of the orbit and destruction of Sgr. Aminimum 8 kpc width of the trailing stream about the Sgr orbital midplane isimplied by verified RV members. The coldness of this stream (dispersion ~10km/s) provides upper limits on the combined contributions of stream heating bya lumpy Galactic halo and the intrinsic dispersion of released stars, which isa function of the Sgr core mass. The Sgr trailing arm is consistent with aGalactic halo containing one dominant, LMC-like lump, however some lumpierhalos are not ruled out. An upper limit to the total M/L of the Sgr core is 21in solar units. A second structure that roughly mimics expectations forwrapped, leading Sgr arm debris crosses the trailing arm in the SouthernHemisphere; however, this may also be an unrelated tidal feature. Among the <13kpc M giants toward the South Galactic Pole are some with large RVs thatidentify them as halo stars, perhaps part of the Sgr leading arm near the Sun.The positions and RVs of Southern Hemisphere M giants are compared with thoseof southern globular clusters potentially stripped from the Sgr system andsupport for association of Pal 2 and Pal 12 with Sgr debris is found. Ourdiscussion includes description of a masked-filtered cross-correlationmethodology that achieves better than 1/20 of a resolution element RVs inmoderate resolution spectra.Comment: 41 pages, 6 figures, Astronomical Journal, in press (submitted Nov.  24, 2003; tentatively scheduled for July 2004 issue

the astronomical journal

A Two Micron All Sky Survey View of the Sagittarius Dwarf Galaxy. II. Swope Telescope Spectroscopy of M Giant Stars in the Dynamically Cold Sagittarius Tidal Stream