A 2MASS ALL-SKY VIEW OF THE SAGITTARIUS DWARF GALAXY. VII. KINEMATICS OF THE MAIN BODY OF THE SAGITTARIUS dSph

Journal Article · Sat Sep 01 04:00:00 EDT 2012 · Astrophysical Journal

DOI:https://doi.org/10.1088/0004-637X/756/1/74· OSTI ID:22092441

Frinchaboy, Peter M. ^[1]; Majewski, Steven R.; Patterson, Richard J. ^[2]; Munoz, Ricardo R. ^[3]; Law, David R. ^[4]; Lokas, Ewa L. ^[5]; Kunkel, William E. ^[6]

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1. Department of Physics and Astronomy, Texas Christian University, TCU Box 298840, Fort Worth, TX 76129 (United States)
2. Department of Astronomy, University of Virginia, P.O. Box 400325, Charlottesville, VA 22904-4325 (United States)
3. Astronomy Department, Yale University, P.O. Box 208101, New Haven, CT 06520-8101 (United States)
4. Dunlap Institute for Astronomy and Astrophysics, University of Toronto, 50 St. George Street, Toronto, Ontario M5S 3H4 (Canada)
5. Nicolaus Copernicus Astronomical Center, Bartycka 18, 00-716 Warsaw (Poland)
6. Las Campanas Observatory, Casilla 601, La Serena (Chile)

We have assembled a large-area spectroscopic survey of giant stars in the Sagittarius (Sgr) dwarf galaxy core. Using medium resolution (R {approx} 15,000), multifiber spectroscopy we have measured velocities of these stars, which extend up to 12 Degree-Sign from the galaxy's center (3.7 core radii or 0.4 times the King limiting radius). From these high-quality spectra we identify 1310 Sgr members out of 2296 stars surveyed, distributed across 24 different fields across the Sgr core. Additional slit spectra were obtained of stars bridging from the Sgr core to its trailing tail. Our systematic, large-area sample shows no evidence for significant rotation, a result at odds with the {approx}20 km s{sup -1} rotation required as an explanation for the bifurcation seen in the Sgr tidal stream; the observed small ({<=}4 km s{sup -1}) velocity trend primarily along the major axis is consistent with models of the projected motion of an extended body on the sky with no need for intrinsic rotation. The Sgr core is found to have a flat velocity dispersion (except for a kinematically colder center point) across its surveyed extent and into its tidal tails, a property that matches the velocity dispersion profiles measured for other Milky Way dwarf spheroidal (dSph) galaxies. We comment on the possible significance of this observed kinematical similarity for the dynamical state of the other classical Milky Way dSphs in light of the fact that Sgr is clearly a strongly tidally disrupted system.

• OSTI ID: 22092441
• Journal Information: Astrophysical Journal, Journal Name: Astrophysical Journal Journal Issue: 1 Vol. 756; ISSN ASJOAB; ISSN 0004-637X
• Country of Publication: United States
• Language: English

Related Subjects

79 ASTRONOMY AND ASTROPHYSICS
ASTRONOMY
ASTROPHYSICS
EMISSION SPECTRA
EMISSION SPECTROSCOPY
GIANT STARS
MILKY WAY
RESOLUTION
ROTATION
SKY
VELOCITY
VISIBLE RADIATION