The search for accreted satellites in the Galactic disk is a challenging task, to which Gaia plays a crucial role in synergy with ground-based spectroscopic surveys. In 2021, P. Re Fiorentin et al. discovered five substructures with disk kinematics including Icarus. To gain more insight into the origin of Icarus as a remnant of a dwarf galaxy rather than a signature of secular processes of disk formation, we complement astrometric Gaia DR3 data with spectroscopy from APOGEE DR17 and GALAH DR3, and explore the chemodynamical distributions within 3 kpc of the Sun. We select 622 stars in the accreted/unevolved regions of [Mg/Mn]–[Al/Fe] and [Mg/Fe]–[Fe/H], where we identify 81 and 376 stars with −2 < [Fe/H] < −0.7 belonging to Icarus and Gaia-Sausage-Enceladus (GSE), respectively. The revised properties of Icarus are: 〈V + VLSR〉 ≃ 171 km s−1, σV ≃ 37 km s−1, 〈e〉 ≃ 0.36, 〈[Fe/H]〉 ≃ −1.35, 〈[Mg/Fe]〉 ≃ +0.27, 〈[Al/Fe]〉 ≃ −0.13, and 〈[Mn/Fe]〉 ≃ −0.39. From the color–magnitude diagram of its members, Icarus appears older than 12 Gyr. Such age and dynamical properties are reminiscent of the metal-weak thick disk. However, detailed chemical analysis in the diagnostic spaces [Ni/Fe]–[(C+N)/O], [Y/Eu]–[Fe/H], [Eu/Mg]–[Fe/H], [Ba/Y]–[Fe/H], and [Ba/Mg]–[Mg/H] evidences that Icarus and GSE occupy the accreted region, well separated from the bulk of in situ disk stars. Updated comparisons with N-body simulations confirm that Icarus’s stars are consistent with the debris of a dwarf galaxy with a stellar mass of ∼109M☉ accreted onto a primordial disk on an initial prograde low-inclination orbit.

中文翻译：

---

重访伊卡洛斯：银河系盘中古老的、缺乏金属的吸积恒星流


在银河系盘中寻找吸积卫星是一项具有挑战性的任务，Gaia 在与地面光谱巡天协同作用方面发挥着至关重要的作用。2021 年，P. Re Fiorentin 等人发现了包括 Icarus 在内的 5 个具有圆盘运动学的子结构。为了更深入地了解伊卡洛斯起源于矮星系的残余物，而不是盘形成的长期过程的特征，我们用 APOGEE DR17 和 GALAH DR3 的光谱学补充了天体测量 Gaia DR3 数据，并探索了距离太阳 3 kpc 以内的化学动力学分布。我们在 [Mg/Mn]–[Al/Fe] 和 [Mg/Fe]–[Fe/H] 的吸积/未演化区域中选择了 622 颗恒星，在那里我们确定了 81 颗和 376 颗恒星，其中 -2 < [Fe/H] < -0.7 分别属于伊卡洛斯和盖亚-香肠-土卫二 （GSE）。伊卡洛斯的修改特性为：〈V + VLSR〉 ≃ 171 km s−1，σV ≃ 37 km s−1，〈e〉 ≃ 0.36，〈[Fe/H]〉 ≃ −1.35，〈[Mg/Fe]〉 ≃ +0.27，〈[Al/Fe]〉 ≃ −0.13，以及〈[Mn/Fe]〉 ≃ −0.39。从其成员体的色星等图来看，伊卡洛斯似乎比 12 吉尔更古老。这样的年龄和动力学特性让人想起金属弱的厚盘。然而，在诊断空间[Ni/Fe]–[（C+N）/O]、[Y/Eu]–[Fe/H]、[Eu/Mg]–[Fe/H]、[Ba/Y]–[Fe/H]和[Ba/Mg]–[Mg/H]中的详细化学分析表明，伊卡洛斯和GSE占据了吸积区域，与大部分原位盘星很好地分开。与 N 体模拟的更新比较证实，伊卡洛斯的恒星与一个矮星系的碎片一致，该星系的恒星质量为 ∼109M☉，吸积在初始顺行低倾角轨道上的原始盘上。