Title: Tidal interaction can stop galactic bars: on the LMC non-rotating bar Show Chinese title

Title: 潮汐相互作用可以阻止星系棒：关于麦哲伦云非旋转棒

Abstract: Context: Using Gaia DR3 data, Jim\'enez-Arranz et al. (2024a) computed the LMC bar pattern speed using three different methods. One of them suggested that the LMC might be hosting a bar that barely rotates, and is slightly counter-rotating with respect to the LMC disc, with a pattern speed of $\Omega_p = -1.0 \pm 0.5$ km/s/kpc. Aims: To confirm that tidal interactions can trigger the LMC hosting a non-rotating bar due to its interaction with the SMC, which could cause the LMC bar to slow down significantly until it (momentarily) stops. Methods: We analyse a subset of models (K9 and K21) from the KRATOS suite (Jim\'enez-Arranz et al. 2024b) where we detected non-rotating bars. We make use of two different methods to track the evolution of the bar pattern speed: the program patternSpeed.py (Dehnen et al. 2023), and temporal finite-differences of the change rate the bar major axis' phase angle. Results: In the second LMC-SMC-like pericenter passage of K9, the bar of the LMC-like galaxy weakens to almost disappear and regenerates with a pattern speed that suffers a slowdown from $\Omega_p \sim 20$ km/s/kpc to $\Omega_p \sim 0$ km/s/kpc in less than 75 Myr. Then, the bar rotates at less than $\Omega_p \sim 3-5$ km/s/kpc for around 100 Myr, until it recovers the initial (before interaction) pattern speed of $\Omega_p \sim 10$ km/s/kpc. The results for the K21 simulation are comparable. Conclusions: This work is the first direct evidence that galactic bars can be slowed down or even stopped by tidal interaction, which strengthens the possibility of the LMC hosting a non-rotating bar, and can add an alternative formation scenario for observed slow-rotating bars. Show Chinese abstract

Abstract: 背景：利用盖亚DR3数据，吉梅内斯-阿里兰兹等人（2024a）使用三种不同的方法计算了大麦哲伦云（LMC）棒的速度。其中一种方法表明，LMC可能正在容纳一个几乎不旋转的棒，并且相对于LMC盘稍有反向旋转，其模式速度为$\Omega_p = -1.0 \pm 0.5$km/s/kpc。 目的：确认潮汐相互作用是否可以触发LMC由于与SMC的相互作用而拥有一个非旋转的棒，这可能导致LMC棒显著减速直至暂时停止。 方法：我们分析了KRATOS集合（吉梅内斯-阿里兰兹等人，2024b）中的子集模型（K9和K21），在这些模型中检测到了非旋转的棒。我们使用两种不同的方法来追踪棒模式速度的变化：程序patternSpeed.py（德嫩等人，2023年），以及棒主轴相角变化率的时间有限差分。 结果： 在K9的第二次类似LMC-SMC近日点通过时，类似LMC星系的棒减弱到几乎消失，并以模式速度从$\Omega_p \sim 20$km/s/kpc减缓至$\Omega_p \sim 0$km/s/kpc，在不到75百万年内重新生成。然后，棒在大约100百万年内旋转速度低于$\Omega_p \sim 3-5$km/s/kpc，直到恢复最初的（交互前）模式速度$\Omega_p \sim 10$km/s/kpc。 K21模拟的结果与此相当。 结论：这项工作首次直接证明了星系棒可以通过潮汐相互作用减速甚至停止，这加强了LMC可能拥有非旋转棒的可能性，并为观测到的慢速旋转棒提供了一种替代形成场景。