标题： 厚盘旋转-金属丰度相关性的证据 显示英文标题

标题： Evidence of a thick disk rotation-metallicity correlation

摘要： 我们分析了一项新的运动学巡天，它包含了从SDSS DR7位置推导出的精确自行，并结合了GSC-II数据库中的多历元测量。 通过SDSS光谱-光度数据（有效温度、表面重力、金属丰度和径向速度），我们估计了27,000颗FGK型（亚）矮星的光度视差，这些星被选为太阳附近几千秒差距内的厚盘和内晕七维空间分布（运动相位分布加上化学丰度）的示踪体，其金属丰度为[Fe/H]<-0.5。 我们发现在距离盘面一到三千万秒差距之间的厚盘恒星中存在运动学与金属丰度的相关性，dVphi/d[Fe/H]=40-50 km/s/dex，而对于丰度-1<[Fe/H]<-0.5的恒星，而当[Fe/H]>-0.5时没有显著的相关性。 此外，我们在厚盘的1千秒差距<|z|<3千秒差距范围内估算了一个浅层的垂直旋转速度梯度，dVphi/d|z|=-19±2 km/s/kpc，并且内晕的低前旋速度为37±3 km/s，直到4千秒差距。 最后，我们简要讨论了这些发现对冷暗物质层次化星系形成机制以及银河盘长期演化过程中的厚盘形成场景的影响。 显示英文摘要

摘要： We analyze a new kinematic survey that includes accurate proper motions derived from SDSS DR7 positions, combined with multi-epoch measurements from the GSC-II database. By means of the SDSS spectro-photometric data (effective temperature, surface gravity, metallicity, and radial velocities), we estimate photometric parallaxes for a sample of 27,000 FGK (sub)dwarfs with [Fe/H]<-0.5, which we adopted as tracers of the seven-dimensional space distribution (kinematic phase distribution plus chemical abundance) of the thick disk and inner halo within a few kiloparsecs of the Sun. We find evidence of a kinematics-metallicity correlation, dVphi/d[Fe/H]=40-50 km/s/dex, amongst thick disk stars located between one and three kiloparsecs from the plane and with abundance -1 <[Fe/H]< -0.5, while no significant correlation is present for [Fe/H]> -0.5. In addition, we estimate a shallow vertical rotation velocity gradient, dVphi/d|z| = -19 +/- 2 km/s/kpc, for the thick disk between 1 kpc < |z| < 3 kpc, and a low prograde rotation, 37 +/- 3 km/s for the inner halo up to 4 kpc. Finally, we briefly discuss the implications of these findings for the thick disk formation scenarios in the context of CDM hierarchical galaxy formation mechanisms and of secular evolutionary processes in galactic disks.