arXivDaily arXiv每日学术速递 周一至周五更新
arXiv 2408.01504astro-ph.GA
收藏

恒星棒在 TNG50 中形成暗物质对应体

Stellar bars form dark matter counterparts in TNG50

Neil Ash, Monica Valluri, Yingtian Chen, Eric F. Bell

AI总结:

本研究在 TNG50 宇宙学模拟中确认有棒盘星系普遍存在更短、弱 75% 的暗物质棒,并提出基于四极系数的模式速度测量方法,揭示恒星棒与暗物质棒长期共线、同速且轴取向进动章动。

摘要:

与恒星棒相伴的暗物质(DM)棒此前已被证明会在孤立盘星系的理想化模拟中形成。在这里,我们表明 DM 棒普遍存在于 TNG50 宇宙学模拟套件中的有棒盘星系内,但不会出现在无棒盘星系中。与孤立模拟一致,DM 棒通常短于其恒星对应体,并且按 Fourier A2 矩测量要弱 75%。DM 棒主导着内晕势的形状,并且很容易在四极系数的时间序列中被识别出来。我们提出了两种利用这些系数测量棒模式速度的新方法,并用它们对位于 TNG50 高时间分辨率子盒之一中的一个样本星系进行了模式速度和自转轴取向的测量。该星系中的恒星棒和暗物质棒在最近 8 Gyr 内始终保持共线,并且全程具有相同的模式速度。棒的模式速度和自转轴取向在最近 8 Gyr 内都发生了显著演化,这与动力学摩擦和气体吸积对棒施加的力矩一致。虽然棒模式速度总体上随时间下降,但在并合之后可以观察到其上升。自转轴并非在时间上保持静止,而是表现出进动和章动,这可能由旋转平面之外的力矩造成。我们发现恒星和 DM 质量分布的形状与棒模式速度紧密相关。

英文摘要:

Dark matter (DM) bars that shadow stellar bars have been previously shown to form in idealized simulations of isolated disk galaxies. Here, we show that DM bars commonly occur in barred disk galaxies in the TNG50 cosmological simulation suite, but do not appear in unbarred disk galaxies. Consistent with isolated simulations, DM bars are typically shorter than their stellar counterparts and are $75\%$ weaker as measured by the Fourier $A_2$ moment. DM bars dominate the shape of the inner halo potential and are easily identified in the time series of quadrupolar coefficients. We present two novel methods for measuring the bar pattern speed using these coefficients, and use them to make a measurement of the pattern speed and rotation axis orientation for one sample galaxy located in one of the high-time resolution subboxes of TNG50. The stellar and dark bars in this galaxy remain co-aligned throughout the last 8 Gyr and have identical pattern speeds throughout. Both the pattern speed and rotation axis orientation of the bars evolve considerably over the last 8 Gyr, consistent with torques on the bars due to dynamical friction and gas accretion. While the bar pattern speed generally decreases over the time course, it is seen to increase after mergers. Rather than remaining static in time, the rotation axis displays both precession and nutation possibly caused by torques outside the plane of rotation. We find that the shape of the stellar and DM mass distributions are tightly correlated with the bar pattern speed.

机构、总结、中文摘要均由AI分析而来,可能存在错误,请以论文正文为准。

↑