Selecting Sagittarius : identification and chemical characterization of the Sagittarius stream

Hyde, E. A. and Keller, S. and Zucker, D. B. and Ibata, R. and Siebert, A. and Lewis, G. F. and Penarrubia, J. and Irwin, M. and Gilmore, G. and Lane, R. R. and Koch, A. and Conn, A. R. and Diakogiannis, F. I. and Martell, S. (2015) Selecting Sagittarius : identification and chemical characterization of the Sagittarius stream. The Astrophysical Journal, 805 (2): 189. ISSN 0004-637X

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1505.07926v1 - Accepted Version
Available under License Creative Commons Attribution.
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Abstract

Wrapping around the Milky Way, the Sagittarius stream is the dominant substructure in the halo. Our statistical selection method has allowed us to identify 106 highly likely members of the Sagittarius stream. Spectroscopic analysis of metallicity and kinematics of all members provides us with a new mapping of the Sagittarius stream. We find correspondence between the velocity distribution of stream stars and those computed for a triaxial model of the Milky Way dark matter halo. The Sagittarius trailing arm exhibits a metallicity gradient, ranging from −0.59 to −0.97 dex over 142°. This is consistent with the scenario of tidal disruption from a progenitor dwarf galaxy that possessed an internal metallicity gradient. We note high metallicity dispersion in the leading arm, causing a lack of detectable gradient and possibly indicating orbital phase mixing. We additionally report on a potential detection of the Sextans dwarf spheroidal in our data.