标题： 平方公里阵列望远镜作为角动量之门 显示英文标题

标题： The SKA as a Doorway to Angular Momentum

摘要： 角动量是支配星系演化的最基础的物理量之一。 恒星/重子质量相同的星系之间颜色、形态、恒星形成率以及气体比例的差异，可能由它们特定的恒星/重子角动量的差异广泛解释。 由于首次出现收敛自旋的星系模拟，以及运动学观测的显著增加，角动量科学的巨大潜力才刚刚被认识到。 然而，这样的观测仍然受到这样一个事实的挑战：大部分恒星/重子角动量位于较大的半径上。 事实上，指数盘中贡献角动量最大的半径（3Re-4Re）是贡献盘质量最大的半径的两倍；因此，为了得到收敛的角动量测量值，需要要么非常深的积分场光谱（IFS）数据，要么选择性地测量自然存在于主导角动量的大盘半径上的中性原子氢（HI）的运动学。 SKA因其能够测量非常大且特征良好的星系样本中的解析和/或整体HI运动学，而有机会成为世界上领先的角动量研究设施。 这些测量将允许，例如， (1)非常稳健地确定星系在(M,j)平面中的二维分布，(2)最大、系统地测量M、j与第三类星系属性之间的关系，以及(3)最精确地测量角动量矢量的大尺度分布和环境依赖性，无论是就范数还是方向而言。 所有这些测量都将代表构建下一代星系演化模型的绝佳工具。 显示英文摘要

摘要： Angular momentum is one of the most fundamental physical quantities governing galactic evolution. Differences in the colours, morphologies, star formation rates and gas fractions amongst galaxies of equal stellar/baryon mass M are potentially widely explained by variations in their specific stellar/baryon angular momentum j. The enormous potential of angular momentum science is only just being realised, thanks to the emergence of the first simulations of galaxies with converged spins, paralleled by a dramatic increase in kinematic observations. Such observations are still challenged by the fact that most of the stellar/baryon angular momentum resides at large radii. In fact, the radius that maximally contributes to the angular momentum of an exponential disk (3Re-4Re) is twice as large as the radius that maximally contributes to the disk mass; thus converged measurements of angular momentum require either extremely deep IFS data or, alternatively, kinematic measurements of neutral atomic hydrogen (HI), which naturally resides at the large disk radii that dominate the angular momentum. The SKA has a unique opportunity to become the world-leading facility for angular momentum studies due to its ability to measure the resolved and/or global HI kinematics in very large and well-characterised galaxy samples. These measurements will allow, for example, (1) a very robust determination of the two-dimensional distribution of galaxies in the (M,j)-plane, (2) the largest, systematic measurement of the relationship between M, j, and tertiary galaxy properties, and (3) the most accurate measurement of the large-scale distribution and environmental dependence of angular momentum vectors, both in terms of norm and orientation. All these measurements will represent exquisite tools to build a next generation of galaxy evolution models.