The tidal evolution of the Fornax dwarf spheroidal and its globular clusters
The tidal evolution of the Fornax dwarf spheroidal and its globular clusters
复制标题
Fornax矮球体及其球状星团的潮汐演化
DOI：
10.1093/mnras/stab2912
复制
发表时间：
2022
影响因子：
4.8
通讯作者：
Borukhovetskaya A
中科院分区：
文献类型：
--
作者：
Borukhovetskaya A
从其运动学推断出的 Fornax 矮椭球星系的暗物质含量远低于 LCDM 宇宙学模拟的预期。我们使用 N 体模拟来检验这是否可能是银河潮汐的结果。我们发现，尽管盖亚任务改进了自行，天炉座的近心距离仍然受到很少的限制，主要是因为它的最大速度分量大致与太阳运动反平行。因此，将 Fornax 的自行运动转化为银河中心速度敏感地依赖于 Fornax 的假设距离：观测到的距离不确定性意味着周心距离在 rperi∼50 和∼150 kpc 之间变化。我们的模拟表明，在该估计的较低范围内，最大圆周速度 Vmax= 40 km s−1（或维里质量，如 LCDM 预期）的 LCDM 子晕将在 10 Gyr 内被潮汐剥离至 Vmax∼ 23 km s−1。这会将 Fornax 恒星半质量半径内的暗质量减少到其初始值的一半左右，使其与观测结果一致。潮汐剥离主要影响天炉座的暗物质晕；它的恒星成分受到的影响很小，在此过程中损失的质量小于其初始质量。我们还探索了银河潮汐对 Fornax 球状星团 (GC) 群的动态摩擦衰减时间的影响，但与单独运行的模型相比，几乎没有发现实质性变化的证据。尽管假设有尖头晕，但初始轨道半径在 1 到 2 kpc 之间的 GC 群体与 Fornax GC 的当前空间分布一致。 Fornax 的暗物质含量和 GC 的空间分布似乎都与一个简单的模型不一致，在这个模型中，Fornax 居住在一个潮汐剥离的尖头冷暗物质晕中。
The dark matter content of the Fornax dwarf spheroidal galaxy inferred from its kinematics is substantially lower than expected from LCDM cosmological simulations. We useN-body simulations to examine whether this may be the result of Galactic tides. We find that, despite improved proper motions from theGaiamission, the pericentric distance of Fornax remains poorly constrained, mainly because its largest velocity component is roughly antiparallel to the solar motion. Translating Fornax’s proper motion into a Galactocentric velocity is, thus, sensitively dependent on Fornax’s assumed distance: the observed distance uncertainty,, implies pericentric distances that vary betweenrperi∼ 50 and ∼150 kpc. Our simulations show that forrperiin the lower range of that estimate, an LCDM subhalo with maximum circular velocityVmax= 40 km s−1(or virial mass, as expected from LCDM) would be tidally stripped toVmax∼ 23 km s−1over 10 Gyr. This would reduce the dark mass within the Fornax stellar half-mass radius to about half its initial value, bringing it into agreement with observations. Tidal stripping affects mainly Fornax’s dark matter halo; its stellar component is affected little, losing less thanof its initial mass in the process. We also explore the effect of Galactic tides on the dynamical friction decay times of Fornax’s population of globular clusters (GCs) and find little evidence for substantial changes, compared with models run in isolation. A population of GCs with initial orbital radii between 1 and 2 kpc is consistent with the present-day spatial distribution of Fornax GCs, despite assuming a cuspy halo. Neither the dark matter content nor the spatial distribution of GCs of Fornax seems inconsistent with a simple model where Fornax inhabits a tidally stripped cuspy cold dark matter halo.