Ursa Major II – reproducing the observed properties through tidal disruption
Ursa Major II – reproducing the observed properties through tidal disruption
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大熊座 II – 通过潮汐破坏再现观察到的特性
DOI：
10.1093/mnras/stt925
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发表时间：
2013
影响因子：
4.8
通讯作者：
M. Blaña
中科院分区：
文献类型：
--
作者：
R.Smith;M. Fellhauer;G. Candlish;R. Wojtak;J. Farias;M. Blaña
最近对矮球体大熊座二号形态的深度光度测量和单个恒星的光谱分析，为其特性提供了许多新的限制。速度色散为 $\sim$6 km s$^{-1}$，并且假设星系是维里化的，质量光比接近 $\sim$2000 - 显然暗物质占主导地位。使用 N 体模拟，我们证明了观测到的光度、椭圆率、不规则形态、速度梯度和速度色散可以通过与潮汐质量损失相关的过程以及在没有暗物质的情况下很好地再现。这些结果凸显了大熊二号暗物质含量测量中存在相当大的不确定性。内潮汐尾和潮汐流的动力学导致观测到的恒星速度色散值被提升至$>$5 km s$^{-1}$（有时$>$20 km s$^{-1}$）。这种效应导致我们模型的速度离散度提高到 UMaII 中的观测值。我们测试了一种迭代拒绝技术，用于从提供了天空位置和视线速度的 UMaII 恒星样本中去除未束缚的恒星。我们发现这种技术在根据这些信息提供准确的束缚质量方面非常有效，并且只有当星系的束缚质量小于其初始质量的 10$%$ 时才会失败。然而，当$$3数量级时可见。此外，我们发现质量测量对视线速度的测量不确定性很敏感。 1-4 km s$^{-1}$ 的测量不确定性会导致质量高估 $\sim$1.3-5.7 倍。
Recent deep photometry of the dwarf spheroidal Ursa Major II's morphology, and spectroscopy of individual stars, have provided a number of new constraints on its properties. With a velocity dispersion $\sim$6 km s$^{-1}$, and under the assumption that the galaxy is virialised, the mass-to-light ratio is found to be approaching $\sim$2000 - apparently heavily dark matter dominated. Using N-Body simulations, we demonstrate that the observed luminosity, ellipticity, irregular morphology, velocity gradient, and the velocity dispersion can be well reproduced through processes associated with tidal mass loss, and in the absence of dark matter. These results highlight the considerable uncertainty that exists in measurements of the dark matter content of Ursa Major II. The dynamics of the inner tidal tails, and tidal stream, causes the observed velocity dispersion of stars to be boosted to values of $>$5 km s$^{-1}$ ($>$20 km s$^{-1}$ at times). This effect is responsible for raising the velocity dispersion of our model to the observed values in UMaII. We test an iterative rejection technique for removing unbound stars from samples of UMaII stars whose positions on the sky, and line-of-sight velocities, are provided. We find this technique is very effective at providing an accurate bound mass from this information, and only fails when the galaxy has a bound mass less than 10$%$ of its initial mass. However when $ $3 orders of magnitude are seen. Additionally we find that mass measurements are sensitive to measurement uncertainty in line-of-sight velocities. Measurement uncertainties of 1-4 km s$^{-1}$ result in mass overestimates by a factor of $\sim$1.3-5.7.
DOI：
10.1086/522672
发表时间：
2007-10
期刊：
The Astrophysical Journal Letters
影响因子：
--
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
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
DOI：
10.1088/2041-8205/712/1/l103
发表时间：
2010-02
期刊：
The Astrophysical Journal Letters
影响因子：
--
作者：
V. Belokurov;M. Walker;N. Evans;G. Gilmore;M. Irwin;D. Just;Sergey E. Koposov;M. Mateo;E. Olszewski;L. Watkins;L. W. IoA;Cambridge;S. Observatory;Tucson;U. Michigan
通讯作者：
V. Belokurov;M. Walker;N. Evans;G. Gilmore;M. Irwin;D. Just;Sergey E. Koposov;M. Mateo;E. Olszewski;L. Watkins;L. W. IoA;Cambridge;S. Observatory;Tucson;U. Michigan