The First Tidally Disrupted Ultra-faint Dwarf Galaxy?: A Spectroscopic Analysis of the Tucana III Stream

Abstract We present a spectroscopic study of the tidal tails and core of the Milky Way satellite Tucana III, collectively referred to as the Tucana III stream, using the 2dF+AAOmega spectrograph on the Anglo-Australian Telescope and the IMACS spectrograph on the Magellan Baade Telescope. In addition...

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Bibliographic Details
Published in:The Astrophysical journal 2018-10, Vol.866 (1), p.22
Main Authors: Li, T. S., Simon, J. D., Kuehn, K., Pace, A. B., Erkal, D., Bechtol, K., Yanny, B., Drlica-Wagner, A., Marshall, J. L., Lidman, C., Balbinot, E., Carollo, D., Jenkins, S., Martínez-Vázquez, C. E., Shipp, N., Stringer, K. M., Vivas, A. K., Walker, A. R., Wechsler, R. H., Abdalla, F. B., Allam, S., Annis, J., Avila, S., Bertin, E., Brooks, D., Buckley-Geer, E., Burke, D. L., Rosell, A. Carnero, Kind, M. Carrasco, Carretero, J., Cunha, C. E., D’Andrea, C. B., Costa, L. N. da, Davis, C., Vicente, J. De, Doel, P., Eifler, T. F., Evrard, A. E., Flaugher, B., Frieman, J., García-Bellido, J., Gaztanaga, E., Gerdes, D. W., Gruen, D., Gruendl, R. A., Gschwend, J., Gutierrez, G., Hartley, W. G., Hollowood, D. L., Honscheid, K., James, D. J., Krause, E., Maia, M. A. G., March, M., Menanteau, F., Miquel, R., Plazas, A. A., Sanchez, E., Santiago, B., Scarpine, V., Schindler, R., Schubnell, M., Sevilla-Noarbe, I., Smith, M., Smith, R. C., Soares-Santos, M., Sobreira, F., Suchyta, E., Swanson, M. E. C., Tarle, G., Tucker, D. L.
Format: Article
Language:English
Subjects:
ASTRONOMY AND ASTROPHYSICS
Astrophysics
Color
Dark energy
dark matter
Dwarf galaxies
galaxies: dwarf
galaxies: individual (Tucana III)
Local Group
Metallicity
Metals
Milky Way
Satellites
Sky surveys (astronomy)
Spectroscopic analysis
Star clusters
Stars & galaxies
stars: abundances
Target recognition
Velocity
Velocity gradient
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Summary:Abstract We present a spectroscopic study of the tidal tails and core of the Milky Way satellite Tucana III, collectively referred to as the Tucana III stream, using the 2dF+AAOmega spectrograph on the Anglo-Australian Telescope and the IMACS spectrograph on the Magellan Baade Telescope. In addition to recovering the brightest nine previously known member stars in the Tucana III core, we identify 22 members in the tidal tails. We observe strong evidence for a velocity gradient of over at least 3° on the sky. Based on the continuity in velocity, we confirm that the Tucana III tails are real tidal extensions of Tucana III. The large velocity gradient of the stream implies that Tucana III is likely on a radial orbit. We successfully obtain metallicities for four members in the core and 12 members in the tails. We find that members close to the ends of the stream tend to be more metal-poor than members in the core, indicating a possible metallicity gradient between the center of the progenitor halo and its edge. The spread in metallicity suggests that the progenitor of the Tucana III stream is likely a dwarf galaxy rather than a star cluster. Furthermore, we find that with the precise photometry of the Dark Energy Survey data, there is a discernible color offset between metal-rich disk stars and metal-poor stream members. This metallicity-dependent color offers a more efficient method to recognize metal-poor targets and will increase the selection efficiency of stream members for future spectroscopic follow-up programs on stellar streams.
ISSN:0004-637X
1538-4357
1538-4357
DOI:10.3847/1538-4357/aadf91