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Title: Chemical Abundance Analysis of Tucana III, the Second r -process Enhanced Ultra-faint Dwarf Galaxy

Abstract

Here, we introduce a chemical abundance analysis of four additional confirmed member stars of Tucana III, a Milky Way satellite galaxy candidate in the process of being tidally disrupted as it is accreted by the Galaxy. Two of these stars are centrally located in the core of the galaxy while the other two stars are located in the eastern and western tidal tails. The four stars have chemical abundance patterns consistent with the one previously studied star in Tucana III: they are moderately enhanced in r-process elements, i.e., they have $$\langle$$[Eu/Fe]$$\rangle$$ ≈ +0.4 dex. The non-neutron-capture elements generally follow trends seen in other dwarf galaxies, including a metallicity spread of 0.44 dex and the expected trend in α-elements, i.e., the lower metallicity stars have higher Ca and Ti abundance. In general, the chemical abundance patterns of these stars suggest that Tucana III was an ultra-faint dwarf galaxy, and not a globular cluster, before being tidally disturbed. As is the case for the one other galaxy dominated by r-pr ocess enhanced stars, Reticulum II, Tucana III’s stellar chemical abundances are consistent with pollution from ejecta produced by a binary neutron star merger, although a different r-process element or dilution gas mass is required to explain the abundances in these two galaxies if a neutron star merger is the sole source of r-process enhancement.

Authors:
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Publication Date:
Research Org.:
Fermi National Accelerator Lab. (FNAL), Batavia, IL (United States)
Sponsoring Org.:
USDOE Office of Science (SC), High Energy Physics (HEP) (SC-25)
Contributing Org.:
DES Collaboration
OSTI Identifier:
1573820
Report Number(s):
FERMILAB-PUB-18-651-AE; arXiv:1812.01022
Journal ID: ISSN 1538-4357; oai:inspirehep.net:1763553
Grant/Contract Number:  
AC02-07CH11359
Resource Type:
Journal Article: Accepted Manuscript
Journal Name:
The Astrophysical Journal (Online)
Additional Journal Information:
Journal Volume: 882; Journal Issue: 2; Journal ID: ISSN 1538-4357
Publisher:
Institute of Physics (IOP)
Country of Publication:
United States
Language:
English
Subject:
79 ASTRONOMY AND ASTROPHYSICS; Chemical abundances; Chemically peculiar stars; Dwarf galaxies

Citation Formats

Marshall, J. L., Hansen, T., Simon, J. D., Li, T. S., Bernstein, R. A., Kuehn, K., Pace, A. B., DePoy, D. L., Palmese, A., Pieres, A., Strigari, L., Drlica-Wagner, A., Bechtol, K., Lidman, C., Nagasawa, D. Q., 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, Vicente, J. De, Desai, S., Doel, P., Eifler, T. F., Flaugher, B., Fosalba, P., Frieman, J., García-Bellido, J., Gaztanaga, E., Gerdes, D. W., Gruendl, R. A., Gschwend, J., Gutierrez, G., Hartley, W. G., Hollowood, D. L., Honscheid, K., Hoyle, B., James, D. J., Kuropatkin, N., Maia, M. A. G., Menanteau, F., Miller, C. J., Miquel, R., Plazas, A. A., Sanchez, E., Santiago, B., Scarpine, V., Schubnell, M., Serrano, S., Sevilla-Noarbe, I., Smith, M., Soares-Santos, M., Suchyta, E., Swanson, M. E. C., Tarle, G., and Wester, W. Chemical Abundance Analysis of Tucana III, the Second r -process Enhanced Ultra-faint Dwarf Galaxy. United States: N. p., 2019. Web. doi:10.3847/1538-4357/ab3653.
Marshall, J. L., Hansen, T., Simon, J. D., Li, T. S., Bernstein, R. A., Kuehn, K., Pace, A. B., DePoy, D. L., Palmese, A., Pieres, A., Strigari, L., Drlica-Wagner, A., Bechtol, K., Lidman, C., Nagasawa, D. Q., 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, Vicente, J. De, Desai, S., Doel, P., Eifler, T. F., Flaugher, B., Fosalba, P., Frieman, J., García-Bellido, J., Gaztanaga, E., Gerdes, D. W., Gruendl, R. A., Gschwend, J., Gutierrez, G., Hartley, W. G., Hollowood, D. L., Honscheid, K., Hoyle, B., James, D. J., Kuropatkin, N., Maia, M. A. G., Menanteau, F., Miller, C. J., Miquel, R., Plazas, A. A., Sanchez, E., Santiago, B., Scarpine, V., Schubnell, M., Serrano, S., Sevilla-Noarbe, I., Smith, M., Soares-Santos, M., Suchyta, E., Swanson, M. E. C., Tarle, G., & Wester, W. Chemical Abundance Analysis of Tucana III, the Second r -process Enhanced Ultra-faint Dwarf Galaxy. United States. doi:10.3847/1538-4357/ab3653.
Marshall, J. L., Hansen, T., Simon, J. D., Li, T. S., Bernstein, R. A., Kuehn, K., Pace, A. B., DePoy, D. L., Palmese, A., Pieres, A., Strigari, L., Drlica-Wagner, A., Bechtol, K., Lidman, C., Nagasawa, D. Q., 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, Vicente, J. De, Desai, S., Doel, P., Eifler, T. F., Flaugher, B., Fosalba, P., Frieman, J., García-Bellido, J., Gaztanaga, E., Gerdes, D. W., Gruendl, R. A., Gschwend, J., Gutierrez, G., Hartley, W. G., Hollowood, D. L., Honscheid, K., Hoyle, B., James, D. J., Kuropatkin, N., Maia, M. A. G., Menanteau, F., Miller, C. J., Miquel, R., Plazas, A. A., Sanchez, E., Santiago, B., Scarpine, V., Schubnell, M., Serrano, S., Sevilla-Noarbe, I., Smith, M., Soares-Santos, M., Suchyta, E., Swanson, M. E. C., Tarle, G., and Wester, W. Mon . "Chemical Abundance Analysis of Tucana III, the Second r -process Enhanced Ultra-faint Dwarf Galaxy". United States. doi:10.3847/1538-4357/ab3653.
@article{osti_1573820,
title = {Chemical Abundance Analysis of Tucana III, the Second r -process Enhanced Ultra-faint Dwarf Galaxy},
author = {Marshall, J. L. and Hansen, T. and Simon, J. D. and Li, T. S. and Bernstein, R. A. and Kuehn, K. and Pace, A. B. and DePoy, D. L. and Palmese, A. and Pieres, A. and Strigari, L. and Drlica-Wagner, A. and Bechtol, K. and Lidman, C. and Nagasawa, D. Q. 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 Vicente, J. De and Desai, S. and Doel, P. and Eifler, T. F. and Flaugher, B. and Fosalba, P. and Frieman, J. and García-Bellido, J. and Gaztanaga, E. and Gerdes, D. W. and Gruendl, R. A. and Gschwend, J. and Gutierrez, G. and Hartley, W. G. and Hollowood, D. L. and Honscheid, K. and Hoyle, B. and James, D. J. and Kuropatkin, N. and Maia, M. A. G. and Menanteau, F. and Miller, C. J. and Miquel, R. and Plazas, A. A. and Sanchez, E. and Santiago, B. and Scarpine, V. and Schubnell, M. and Serrano, S. and Sevilla-Noarbe, I. and Smith, M. and Soares-Santos, M. and Suchyta, E. and Swanson, M. E. C. and Tarle, G. and Wester, W.},
abstractNote = {Here, we introduce a chemical abundance analysis of four additional confirmed member stars of Tucana III, a Milky Way satellite galaxy candidate in the process of being tidally disrupted as it is accreted by the Galaxy. Two of these stars are centrally located in the core of the galaxy while the other two stars are located in the eastern and western tidal tails. The four stars have chemical abundance patterns consistent with the one previously studied star in Tucana III: they are moderately enhanced in r-process elements, i.e., they have $\langle$[Eu/Fe]$\rangle$ ≈ +0.4 dex. The non-neutron-capture elements generally follow trends seen in other dwarf galaxies, including a metallicity spread of 0.44 dex and the expected trend in α-elements, i.e., the lower metallicity stars have higher Ca and Ti abundance. In general, the chemical abundance patterns of these stars suggest that Tucana III was an ultra-faint dwarf galaxy, and not a globular cluster, before being tidally disturbed. As is the case for the one other galaxy dominated by r-pr ocess enhanced stars, Reticulum II, Tucana III’s stellar chemical abundances are consistent with pollution from ejecta produced by a binary neutron star merger, although a different r-process element or dilution gas mass is required to explain the abundances in these two galaxies if a neutron star merger is the sole source of r-process enhancement.},
doi = {10.3847/1538-4357/ab3653},
journal = {The Astrophysical Journal (Online)},
issn = {1538-4357},
number = 2,
volume = 882,
place = {United States},
year = {2019},
month = {9}
}

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