Minniti Dante, Borissova Jura, Rejkuba Marina, Alves David R, Cook Kem H, Freeman Kenneth C
Department of Astronomy, Pontificia Universidad Católica, Aveñida Vicuña Mackenna 4860, Casilla 306, Santiago 22, Chile.
Science. 2003 Sep 12;301(5639):1508-10. doi: 10.1126/science.1088529.
The oldest and most metal-poor Milky Way stars form a kinematically hot halo, which motivates the two major formation scenarios for our galaxy: extended hierarchical accretion and rapid collapse. RR Lyrae stars are excellent tracers of old and metal-poor populations. We measured the kinematics of 43 RR Lyrae stars in the inner regions of the nearby Large Magellanic Cloud (LMC) galaxy. The velocity dispersion equals 53 +/- 10 kilometers per second, which indicates that a kinematically hot metal-poor old halo also exists in the LMC. This result suggests that our galaxy and smaller late-type galaxies such as the LMC have similar early formation histories.
银河系中最古老且金属含量最低的恒星形成了一个运动学上温度较高的晕，这推动了关于我们星系的两种主要形成场景：扩展的层级吸积和快速坍缩。天琴座RR型变星是古老且金属含量低的恒星群体的优秀示踪天体。我们测量了附近大麦哲伦星系（LMC）内部区域43颗天琴座RR型变星的运动学特征。速度弥散等于每秒53±10千米，这表明LMC中也存在一个运动学上温度较高、金属含量低的古老晕。这一结果表明，我们的星系以及像LMC这样较小的晚型星系有着相似的早期形成历史。
