Gaia Reveals a Metal-rich, in situ Component of the Local Stellar Halo

被引:140
作者
Bonaca, Ana [1 ]
Conroy, Charlie [1 ]
Wetzel, Andrew [2 ,3 ,4 ]
Hopkins, Philip F. [2 ]
Keres, Dusan [5 ]
机构
[1] Harvard Univ, Dept Astron, Cambridge, MA 02138 USA
[2] CALTECH, TAPIR, Pasadena, CA 91125 USA
[3] Observ Carnegie Inst Sci, Pasadena, CA USA
[4] Univ Calif Davis, Dept Phys, Davis, CA 95616 USA
[5] Univ Calif San Diego, Dept Phys, Ctr Astrophys & Space Sci, La Jolla, CA 92093 USA
基金
加拿大自然科学与工程研究理事会; 澳大利亚研究理事会; 欧洲研究理事会; 美国安德鲁·梅隆基金会; 美国国家科学基金会; 瑞士国家科学基金会;
关键词
Galaxy: abundances; Galaxy: formation; Galaxy: halo; Galaxy: kinematics and dynamics; Galaxy: structure; solar neighborhood; VELOCITY EXPERIMENT RAVE; MILKY-WAY TOMOGRAPHY; GLOBULAR-CLUSTERS; SOLAR NEIGHBORHOOD; GALAXY FORMATION; DEBRIS STREAMS; THICK DISKS; F-DWARF; STARS; EVOLUTION;
D O I
10.3847/1538-4357/aa7d0c
中图分类号
P1 [天文学];
学科分类号
0704 ;
摘要
We use the first Gaia data release, combined with the RAVE and APOGEE spectroscopic surveys, to investigate the origin of halo stars within. less than or similar to 3 kpc from the Sun. We identify halo stars kinematically as moving at a relative speed of at least 220 km s(-1) with respect to the local standard of rest. These stars are generally less metal-rich than the disk, but surprisingly, half of our halo sample is comprised of stars with [Fe/H] > -1. The orbital directions of these metal-rich halo stars are preferentially aligned with the disk rotation, in sharp contrast with the intrinsically isotropic orbital distribution of the metal-poor halo stars. We find similar properties in the Latte cosmological zoom-in simulation of a Milky Way-like galaxy from the FIRE project. In Latte, metal-rich halo stars formed primarily inside of the solar circle, whereas lower-metallicity halo stars preferentially formed at larger distances (extending beyond the virial radius). This suggests that metal-rich halo stars in the solar neighborhood actually formed in situ within the Galactic disk, rather than having been accreted from satellite systems. These stars, currently on halo-like orbits, therefore have likely undergone substantial radial migration/heating.
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页数:15
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