The Elongated Structure of the Hercules Dwarf Spheroidal Galaxy from Deep Large Binocular Telescope Imaging
The Elongated Structure of the Hercules Dwarf Spheroidal Galaxy from Deep Large Binocular Telescope Imaging
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DOI：
10.1086/522672
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发表时间：
2007-10
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通讯作者：
M. Coleman;J. D. Jong;N. Martin;H. Rix;D. Sand;E. Bell;R. Pogge;D. Thompson;H. Hippelein;E. Giallongo;R. Ragazzoni;A. DiPaola;J. Farinato;R. Smareglia;V. Testa;J. Bechtold;J. Hill;P. Garnavich;R. Green
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作者：
M. Coleman;J. D. Jong;N. Martin;H. Rix;D. Sand;E. Bell;R. Pogge;D. Thompson;H. Hippelein;E. Giallongo;R. Ragazzoni;A. DiPaola;J. Farinato;R. Smareglia;V. Testa;J. Bechtold;J. Hill;P. Garnavich;R. Green
我们提出了一个深，宽视场测光调查新发现的武仙座矮球状星系（dSph），大双筒望远镜的数据的基础上。B、V和r中的图像由大双目照相机获得，覆盖23′ × 23′视场，大小约为25.5（5 σ）。这使得可以在武仙座主序星关闭点以下约1.5等的位置绘制出色星等图。三过滤测光使我们能够优先选择可能的武仙座成员星，并检查这个系统的结构在以前没有达到的水平。我们发现武仙座矮星是高度拉长的（3：1），比银河系的任何其他dSph卫星都要长得多，除了破坏性的人马座矮星。虽然我们不能排除这种不寻常的结构是武仙座作为一个平衡系统所固有的，但我们的研究结果表明，潮汐破裂可能是这种高度椭圆形结构的原因。考虑到这个系统相对较大的银河系中心距离（132 ± 12 kpc），潮汐破裂的迹象需要武仙座矮星在银河系周围的高度偏心轨道上。
We present a deep, wide-field photometric survey of the newly discovered Hercules dwarf spheroidal galaxy (dSph), based on data from the Large Binocular Telescope. Images in B, V, and r were obtained with the Large Binocular Camera covering a 23′ × 23′ field of view to a magnitude of ~25.5 (5 σ). This permitted the construction of color-magnitude diagrams that reach approximately 1.5 mag below the Hercules main-sequence turnoff. Three-filter photometry allowed us to preferentially select probable Hercules member stars and to examine the structure of this system at a previously unattained level. We find that the Hercules dwarf is highly elongated (3 : 1), considerably more so than any other dSph satellite of the Milky Way, except the disrupting Sagittarius dwarf. Although we cannot rule out that the unusual structure is intrinsic to Hercules as an equilibrium system, our results suggest tidal disruption as a likely cause of this highly elliptical structure. Given the relatively large galactocentric distance of this system (132 ± 12 kpc), signs of tidal disruption would require the Hercules dwarf to be on a highly eccentric orbit around the Milky Way.