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

Abstract

In this paper, 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 $$8.0\pm 0.4\,\mathrm{km}\,{{\rm{s}}}^{-1}\,{\deg }^{-1}$$ 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. Lastly, 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.

Authors:
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Publication Date:
Research Org.:
Oak Ridge National Lab. (ORNL), Oak Ridge, TN (United States); SLAC National Accelerator Lab., Menlo Park, CA (United States); Fermi National Accelerator Lab. (FNAL), Batavia, IL (United States)
Sponsoring Org.:
USDOE Office of Science (SC), Advanced Scientific Computing Research (ASCR) (SC-21); USDOE Office of Science (SC), High Energy Physics (HEP) (SC-25)
Contributing Org.:
DES Collaboration
OSTI Identifier:
1479702
Alternate Identifier(s):
OSTI ID: 1484469; OSTI ID: 1490354
Report Number(s):
arXiv:1804.07761; FERMILAB-PUB-18-107-AE-PPD
Journal ID: ISSN 1538-4357
Grant/Contract Number:  
AC05-00OR22725; AC02-07CH11359; AC02-76SF00515
Resource Type:
Journal Article: Accepted Manuscript
Journal Name:
The Astrophysical Journal (Online)
Additional Journal Information:
Journal Volume: 866; Journal Issue: 1; Journal ID: ISSN 1538-4357
Publisher:
Institute of Physics (IOP)
Country of Publication:
United States
Language:
English
Subject:
79 ASTRONOMY AND ASTROPHYSICS; dark matter; galaxies: dwarf; galaxies: individual (Tucana III); Local Group; stars: abundances

Citation Formats

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., and Tucker, D. L. The First Tidally Disrupted Ultra-faint Dwarf Galaxy?: A Spectroscopic Analysis of the Tucana III Stream. United States: N. p., 2018. Web. doi:10.3847/1538-4357/aadf91.
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. The First Tidally Disrupted Ultra-faint Dwarf Galaxy?: A Spectroscopic Analysis of the Tucana III Stream. United States. doi:10.3847/1538-4357/aadf91.
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., and Tucker, D. L. Fri . "The First Tidally Disrupted Ultra-faint Dwarf Galaxy?: A Spectroscopic Analysis of the Tucana III Stream". United States. doi:10.3847/1538-4357/aadf91.
@article{osti_1479702,
title = {The First Tidally Disrupted Ultra-faint Dwarf Galaxy?: A Spectroscopic Analysis of the Tucana III Stream},
author = {Li, T. S. and Simon, J. D. and Kuehn, K. and Pace, A. B. and Erkal, D. and Bechtol, K. and Yanny, B. and Drlica-Wagner, A. and Marshall, J. L. and Lidman, C. and Balbinot, E. and Carollo, D. and Jenkins, S. and Martínez-Vázquez, C. E. and Shipp, N. and Stringer, K. M. and Vivas, A. K. and Walker, A. R. and Wechsler, R. H. and Abdalla, F. B. and Allam, S. and Annis, J. and Avila, S. and Bertin, E. and Brooks, D. and Buckley-Geer, E. and Burke, D. L. and Rosell, A. Carnero and Kind, M. Carrasco and Carretero, J. and Cunha, C. E. and D’Andrea, C. B. and Costa, L. N. da and Davis, C. and Vicente, J. De and Doel, P. and Eifler, T. F. and Evrard, A. E. and Flaugher, B. and Frieman, J. and García-Bellido, J. and Gaztanaga, E. and Gerdes, D. W. and Gruen, D. and Gruendl, R. A. and Gschwend, J. and Gutierrez, G. and Hartley, W. G. and Hollowood, D. L. and Honscheid, K. and James, D. J. and Krause, E. and Maia, M. A. G. and March, M. and Menanteau, F. and Miquel, R. and Plazas, A. A. and Sanchez, E. and Santiago, B. and Scarpine, V. and Schindler, R. and Schubnell, M. and Sevilla-Noarbe, I. and Smith, M. and Smith, R. C. and Soares-Santos, M. and Sobreira, F. and Suchyta, E. and Swanson, M. E. C. and Tarle, G. and Tucker, D. L.},
abstractNote = {In this paper, 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 $8.0\pm 0.4\,\mathrm{km}\,{{\rm{s}}}^{-1}\,{\deg }^{-1}$ 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. Lastly, 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.},
doi = {10.3847/1538-4357/aadf91},
journal = {The Astrophysical Journal (Online)},
issn = {1538-4357},
number = 1,
volume = 866,
place = {United States},
year = {2018},
month = {10}
}

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