The First Tidally Disrupted Ultra-faint Dwarf Galaxy?: A Spectroscopic Analysis of the Tucana III Stream
The First Tidally Disrupted Ultra-faint Dwarf Galaxy?: A Spectroscopic Analysis of the Tucana III Stream
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DOI：
10.3847/1538-4357/aadf91
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发表时间：
2018-04
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通讯作者：
T. Li;J. Simon;K. Kuehn;A. Pace;D. Erkal;K. Bechtol;B. Yanny;A. Drlica-Wagner;J. Marshall;C. Lidman;E. Balbinot;D. Carollo;S. Jenkins;C. Martínez-Vázquez;N. Shipp;K. Stringer;A. K. Vivas;A. Walker;Risa Wechsler;F. Abdalla;S. Allam;J. Annis;S. Ávila;E. Bertin;D. Brooks;E. Buckley-Geer;D. Burke;A. Rosell;M. Kind;J. Carretero;C. Cunha;C. D'Andrea;L. Costa;C. Davis;J. Vicente;P. Doel;T. Eifler;A. Evrard;B. Flaugher;J. Frieman;J. García-Bellido;E. Gaztañaga;D. Gerdes;D. Gruen;R. Gruendl;J. Gschwend;G. Gutiérrez;W. Hartley;D. Hollowood;K. Honscheid;D. James;E. Krause;M. Maia;M. March;F. Menanteau;R. Miquel;A. Plazas;E. Sánchez;B. Santiago;V. Scarpine;R. Schindler;M. Schubnell;I. Sevilla-Noarbe;M. Smith;R. C. Smith;M. Soares-Santos;F. Sobreira;E. Suchyta;M. Swanson;G. Tarlé;D. Tucker
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作者：
T. Li;J. Simon;K. Kuehn;A. Pace;D. Erkal;K. Bechtol;B. Yanny;A. Drlica-Wagner;J. Marshall;C. Lidman;E. Balbinot;D. Carollo;S. Jenkins;C. Martínez-Vázquez;N. Shipp;K. Stringer;A. K. Vivas;A. Walker;Risa Wechsler;F. Abdalla;S. Allam;J. Annis;S. Ávila;E. Bertin;D. Brooks;E. Buckley-Geer;D. Burke;A. Rosell;M. Kind;J. Carretero;C. Cunha;C. D'Andrea;L. Costa;C. Davis;J. Vicente;P. Doel;T. Eifler;A. Evrard;B. Flaugher;J. Frieman;J. García-Bellido;E. Gaztañaga;D. Gerdes;D. Gruen;R. Gruendl;J. Gschwend;G. Gutiérrez;W. Hartley;D. Hollowood;K. Honscheid;D. James;E. Krause;M. Maia;M. March;F. Menanteau;R. Miquel;A. Plazas;E. Sánchez;B. Santiago;V. Scarpine;R. Schindler;M. Schubnell;I. Sevilla-Noarbe;M. Smith;R. C. Smith;M. Soares-Santos;F. Sobreira;E. Suchyta;M. Swanson;G. Tarlé;D. Tucker
我们提出了一个光谱研究的潮汐尾巴和核心的银河系卫星Tucana III，统称为Tucana III流，使用2dF+AAOmega摄谱仪上的英澳望远镜和IMACS摄谱仪上的麦哲伦巴德望远镜。除了恢复最亮的9个以前已知的成员星在杜鹃III核心，我们确定了22个成员的潮汐尾巴。我们观察到了强有力的证据，表明天空中的速度梯度至少超过3°。基于速度的连续性，我们确认Tucana III尾是Tucana III的真实的潮汐延伸。气流的速度梯度很大，这意味着图卡纳三号可能是在径向轨道上。我们成功地获得了4个成员的核心和12个成员的尾巴的金属丰度。我们发现，成员接近流的两端往往是更贫金属比成员的核心，表明可能的金属丰度梯度之间的中心的祖晕和它的边缘。金属丰度的分布表明，图卡纳III流的前身可能是一个矮星系，而不是一个星星团。此外，我们发现，与精确的测光的暗能量调查数据，有一个可辨别的颜色之间的偏移富金属盘星和贫金属流成员。这种金属性依赖的颜色提供了一种更有效的方法来识别金属贫乏的目标，并将提高流成员的选择效率，用于未来恒星流的光谱后续计划。
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.