AAS 203rd Meeting, January 2004
Session 112 The Milky Way and Its Environs
Poster, Thursday, January 8, 2004, 9:20am-4:00pm, Grand Hall

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[112.01] The Kinematic Signature of the Sagittarius Dwarf Galaxy Tidal Debris from SDSS-DR1

R. Wilhelm (Texas Tech), T.C. Beers (Michigan State University), C. Allende Prieto (Univ. of Texas), H. Newberg (RPI), B. Yanny (FNAL)

Recent results from the Sloan Digital Sky Survey (SDSS) and the 2MASS All-Sky Survey have clearly revealed the extent of the spatial distribution of stars affiliated with the tidal debris tail of the Sagittarius Dwarf Galaxy (Sgr). Although these surveys help to constrain the shape of the Sgr orbit, kinematics of the tidal tail stars are crucial in order to fully characterize the structure and dynamics of this component of our Galactic halo, and to allow a better determination of the shape of the Milky Way dark matter halo.

We present kinematic results for a sample of horizontal-branch stars from the SDSS-DR1 spectroscopic data. SDSS photometry and spectroscopy were used to determine the stellar parameters (Teff, log g, [Fe/H]) and subsequent luminosity classification. Distances and radial velocities for a sample of blue horizontal-branch stars were analyzed in the direction of the leading Northern tidal arm located at (b,l) ~ (350, 50) and the trailing southern arc at (b, l) ~ (157, -58). There exists clear evidence of kinematic substructure in both directions. The data match quite well the distribution of carbon stars and model predictions of Ibata et. al (2001 ApJ 551, 2941). This includes the velocity dispersion in the northern arm, where we find \sigma = 55 km/s, and evidence for a bi-modal distribution in the southern arc field, with the dominant component having a very small velocity dispersion, \sigma = 30 km/s. These results are consistent with a more spherical dark matter halo (qm = 0.9) as found by Ibata et. al.

Partial support has been received for this work from NSF grants AST 00-98508 and AST 00-98549.

The author(s) of this abstract have provided an email address for comments about the abstract: ron.wilhelm@ttu.edu

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Bulletin of the American Astronomical Society, 35#5
© 2003. The American Astronomical Soceity.