Energy wrinkles and phase-space folds of the last major merger
Energy wrinkles and phase-space folds of the last major merger
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上次重大合并的能量皱纹和相空间折叠
DOI：
10.1093/mnras/stac3436
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发表时间：
2023
影响因子：
4.8
通讯作者：
Belokurov V
中科院分区：
文献类型：
--
作者：
Belokurov V
依靠theGaiaData Release 3提供的具有完整6D相空间信息的恒星数量的急剧增加，我们解决了太阳周围恒星晕的分布，以揭示不完全相混合的特征。我们发现，对于可能属于最后一次大规模合并的恒星，（vr，r）分布包含一系列长而细的人字形超密度。这些相空间子结构被预测在卫星解体后出现，当它的潮汐碎片有时间卷起、变薄和折叠时。这种人字形以前曾在外部星系中发现过;在这里，我们报告了我们银河系中的第一次检测。我们还表明，观测到的角动量Lz分布出现在高能量，可能揭示了在下降的星系的原始轨道角动量。碎片的能量分布是强烈不对称的，在低E处有一个峰值--我们推测，这可能是矮星快速下沉的证据--并且布满了皱纹和隆起。我们表明，类似的相空间和（E，LZ）子结构存在于星系相互作用的数值模拟中，无论是在bespokeN体运行和宇宙流体动力学放大套件。这里发现的祖先破坏的残留痕迹和正在进行的相位混合的特征不仅有助于限制我们银河系最重要的相互作用的性质，而且可以用作绘制银河系当前引力势及其扰动的新工具。
Relying on the dramatic increase in the number of stars with full 6D phase-space information provided by theGaiaData Release 3, we resolve the distribution of the stellar halo around the Sun to uncover signatures of incomplete phase-mixing. We show that, for the stars likely belonging to the last massive merger, the (vr,r) distribution contains a series of long and thin chevron-like overdensities. These phase-space substructures have been predicted to emerge following the dissolution of a satellite, when its tidal debris is given time to wind up, thin out, and fold. Such chevrons have been spotted in external galaxies before; here, we report the first detection in our own Milky Way. We also show that the observed angular momentumLzdistribution appears more prograde at high energies, possibly revealing the original orbital angular momentum of the in-falling galaxy. The energy distribution of the debris is strongly asymmetric with a peak at lowE– which, we surmise, may be evidence of the dwarf’s rapid sinking – and riddled with wrinkles and bumps. We demonstrate that similar phase-space and (E, Lz) substructures are present in numerical simulations of galaxy interactions, both in bespokeN-body runs and in cosmological hydrodynamical zoom-in suites. The remnant traces of the progenitor’s disruption and the signatures of the on-going phase-mixing discovered here will not only help to constrain the properties of our Galaxy’s most important interaction, but also can be used as a novel tool to map out the Milky Way’s current gravitational potential and its perturbations.