Orbits and Origins of the Young Stars in the Central Parsec
Orbits and Origins of the Young Stars in the Central Parsec
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中央秒差距年轻恒星的轨道和起源
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发表时间：
2006
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通讯作者：
E. Becklin
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作者：
Jessica R. Lu;A. Ghez;S. Hornstein;M. Morris;K. Matthews;David H. Thompson;E. Becklin
我们根据凯克望远镜10年来的有限衍射数据，为银河系中心的大质量年轻恒星提供了新的自行。我们的自行测量现在只有1-2公里/S的不确定度，并允许我们探索居住在超大质量黑洞近光球内的年轻恒星的起源，其强大的潮汐力量使该地区不适合恒星形成。然而，它们的存在可以被解释为在吸积盘中原位形成恒星，或者是通过动力摩擦螺旋进入的大质量星团的残余物。早期的恒星速度矢量被用来假设所有年轻恒星都位于两个相反旋转的恒星盘中，这与上述两种形成情景都是一致的。我们的精确自身运动第一次使我们能够确定每一颗恒星的轨道参数，从而检验大质量恒星位于两个恒星盘中的假设。在这项研究中之前提出的26颗年轻恒星中，我们发现几乎所有的恒星都表现出与这样一个圆盘一致的轨道约束。另一方面，在这项研究中先前提出的位于外层、定义较差的逆时针盘的7颗恒星中，有6颗表现出与这样的盘不一致的倾斜度，这让人对外盘的存在产生了疑问。此外，对于内盘中有偏心率约束的恒星，我们发现有几颗恒星的偏心率下限超过0.4，这意味着高度偏心的轨道。这与简单的吸积盘形成情景形成对比，后者通常预测的主要是圆形轨道。
We present new proper motions for the massive, young stars at the Galactic Center, based on 10 years of diffraction limited data from the Keck telescopes. Our proper motion measurements now have uncertainties of only 1-2 km/s and allow us to explore the origin of the young stars that reside within the sphere of inflience of the supermassive black hole whose strong tidal forces make this region inhospitable for star formation. Their presence, however, may be explained either by in situ star formation in an accretion disk or as the remnants of a massive stellar cluster which spiraled in via dynamical friction. Earlier stellar velocity vectors were used to postulate that all the young stars resided in two counter-rotating stellar disks, which is consistent with both of the above formation scenarios. Our precise proper motions allow us, for the frst time, to determine the orbital parameters of each individual star and thereby to test the hypothesis that the massive stars reside in two stellar disks. Of the 26 young stars in this study that were previously proposed to lie on the inner, clockwise disk, we find that nearly all exhibit orbital constraints consistent with such a disk. On the other hand, of the 7 stars in this study previously proposed to lie in the outer, less well-defhed counter-clockwise disk, 6 exhibit inclinations that are inconsistent with such a disk, bringing into question the existence of the outer disk. Furthermore, for stars in the inner disk that have eccentricity constraints, we find several that have lower limits to the eccentricity of more than 0.4, implying highly eccentric orbits. This stands in contrast to simple accretion disk formation scenarios which typically predict predominantly circular orbits.