Triangulum II. Not Especially Dense After All
Triangulum II. Not Especially Dense After All
复制标题
三角二号。
DOI：
--
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发表时间：
2017
期刊：
影响因子：
--
通讯作者：
G. Duggan
中科院分区：
文献类型：
--
作者：
E. Kirby;J. Cohen;J. Simon;P. Guhathakurta;A. Thygesen;G. Duggan
在过去三年发现的银河系卫星中，三角座II在揭示其动力学状态方面表现出最大的困难。柯比等人认为它是已知的暗物质最多的星系，质量与光的比例在半光半径内。另一方面，马丁等人测量到的外部速度色散比中心速度色散大3.5 ± 2.1倍，这表明系统可能不处于平衡状态。根据Keck/DEIMOS对三角座II中13颗成员星的新的多历元测量，我们将速度色散限制为km s−1（90% C.L.）。我们之前的测量是基于六颗恒星，由于存在一颗径向速度可变的双星星星而膨胀。我们发现没有证据表明，速度色散随半径增加。这些恒星显示出广泛的金属丰度，表明三角座II保留了超新星喷出物，因此拥有或曾经拥有大量的暗物质晕。然而，金属丰度分散的检测取决于两个最富金属的恒星的成员。其恒星质量低于平均恒星金属量相近的星系，这可能表明三角座II要么是一个星星团，要么是一个潮汐剥离的矮星系。其中一颗星星的详细丰度显示出严重的中子捕获丰度，类似于大多数其他超暗矮星系中的恒星，但不同于球状星团中的恒星。
Among the Milky Way satellites discovered in the past three years, Triangulum II has presented the most difficulty in revealing its dynamical status. Kirby et al. identified it as the most dark-matter-dominated galaxy known, with a mass-to-light ratio within the half-light radius of . On the other hand, Martin et al. measured an outer velocity dispersion that is 3.5 ± 2.1 times larger than the central velocity dispersion, suggesting that the system might not be in equilibrium. From new multi-epoch Keck/DEIMOS measurements of 13 member stars in Triangulum II, we constrain the velocity dispersion to be km s−1 (90% C.L.). Our previous measurement of , based on six stars, was inflated by the presence of a binary star with variable radial velocity. We find no evidence that the velocity dispersion increases with radius. The stars display a wide range of metallicities, indicating that Triangulum II retained supernova ejecta and therefore possesses, or once possessed, a massive dark matter halo. However, the detection of a metallicity dispersion hinges on the membership of the two most metal-rich stars. The stellar mass is lower than galaxies of similar mean stellar metallicity, which might indicate that Triangulum II is either a star cluster or a tidally stripped dwarf galaxy. Detailed abundances of one star show heavily depressed neutron-capture abundances, similar to stars in most other ultra-faint dwarf galaxies but unlike stars in globular clusters.
DOI：
10.1088/0004-637x/780/1/91
发表时间：
2013-11
期刊：
The Astrophysical Journal
影响因子：
--
作者：
A. Koch;T. Hansen;S. Feltzing;M. Wilkinson
通讯作者：
A. Koch;T. Hansen;S. Feltzing;M. Wilkinson
影响因子：
6.5
作者：
Feltzing;Matteucci
通讯作者：
Matteucci