Orbital Support and Evolution of Flat Profiles of Bars (Shoulders)
Orbital Support and Evolution of Flat Profiles of Bars (Shoulders)
复制标题
DOI：
10.3847/1538-4357/ace976
复制
发表时间：
2023-03
期刊：
影响因子：
--
通讯作者：
Leandro Beraldo e Silva;V. Debattista;S. Anderson;M. Valluri;P. Erwin;Kathryne J. Daniel;N. Deg
中科院分区：
文献类型：
--
作者：
Leandro Beraldo e Silva;V. Debattista;S. Anderson;M. Valluri;P. Erwin;Kathryne J. Daniel;N. Deg
许多棒状星系在其棒长轴密度剖面上呈现上凸（肩）。模拟研究表明，肩由环形x 1轨道支撑，发生在生长中的杆中，并且可能在杆屈曲后出现。我们通过模拟中轨道的频率分析来研究轨道支持和肩部的演化。我们证实，环状轨道可以支撑肩部，并且在垂直加厚后可以在较小程度上保持这种状态。我们发现环状轨道出现在共振（Ω φ−ΩP）/Ω R = 1/2（类似于经典的内Lindblad共振，这里称为ILR）处，其垂直与径向频率比为1 > Ω z /Ω R > 3/2（垂直热轨道）。ILR的冷轨道（Ω z /Ω R > 3/2）垂直较薄，没有环，对肩的贡献可以忽略不计。随着棒子变慢变厚，要么是特别变厚，要么是弯曲变厚，它们就会聚集在ILR的温暖轨道上。进一步的增厚将这些轨道带向穿过垂直ILR [vILR， （Ω φ−ΩP）/Ω z = 1/2]，在那里它们将平面内运动转换为垂直运动，变得混乱，运动学上更热，肩部支撑更少。因此，持久的肩需要条状物来捕获新星，这与不断增长的条状物的需求是一致的。由于屈曲加速了在ILR的热轨道上的捕获，因此可以在模拟中看到，它可以随后形成肩。这一序列支持了最近的观测发现，即肩部可能先于bp隆起的出现。提供了用于频率分析的python模块naif。
Many barred galaxies exhibit upturns (shoulders) in their bar-major-axis density profile. Simulation studies have suggested that shoulders are supported by looped x 1 orbits, occur in growing bars, and can appear after bar buckling. We investigate the orbital support and evolution of shoulders via frequency analyses of orbits in simulations. We confirm that looped orbits are shoulder-supporting, and can remain so, to a lesser extent, after being vertically thickened. We show that looped orbits appear at the resonance ( Ω φ − ΩP)/Ω R = 1/2 (analogous to the classical inner Lindblad resonance, and here called ILR) with vertical-to-radial frequency ratios 1 ≲ Ω z /Ω R ≲ 3/2 (vertically warm orbits). Cool orbits at the ILR (those with Ω z /Ω R > 3/2) are vertically thin and have no loops, contributing negligibly to shoulders. As bars slow and thicken, either secularly or by buckling, they populate warm orbits at the ILR. Further thickening carries these orbits toward crossing the vertical ILR [vILR, ( Ω φ − ΩP)/Ω z = 1/2], where they convert in-plane motion to vertical motion, become chaotic, kinematically hotter, and less shoulder-supporting. Hence, persistent shoulders require bars to trap new stars, consistent with the need for a growing bar. Since buckling speeds up trapping on warm orbits at the ILR, it can be followed by shoulder formation, as seen in simulations. This sequence supports the recent observational finding that shoulders likely precede the emergence of BP-bulges. The python module for the frequency analysis, naif, is made available.