Extreme kinematic misalignment in IllustrisTNG galaxies: the origin, structure, and internal dynamics of galaxies with a large-scale counterrotation

S. Khoperskov, I. Zinchenko, Branislav Avramov, S. Khrapov, P. Berczik, A. Saburova, M. A. Ishchenko, A. Khoperskov, C. Pulsoni, Yulia A. Venichenko, D. Bizyaev, A. Moiseev
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引用次数: 14

Abstract

Modern galaxy formation theory suggests that the misalignment between stellar and gaseous components usually results from an external gas accretion and/or interaction with other galaxies. The extreme case of the kinematic misalignment is demonstrated by so-called galaxies with counterrotation that possess two distinct components rotating in opposite directions with respect to each other. We provide an in-deep analysis of galaxies with counterrotation from IllustrisTNG100 cosmological simulations. We have found $25$ galaxies with substantial stellar counterrotation in the stellar mass range of $2\times10^{9}-3\times10^{10}$~\Msun. In our sample the stellar counterrotation is a result of an external gas infall happened $\approx 2-8$~Gyr ago. The infall leads to the initial removal of pre-existing gas, which is captured and mixed together with the infalling component. The gas mixture ends up in the counterrotating gaseous disc. We show that $\approx 90\%$ of the stellar counterrotation formed in-situ, in the counterrotating gas. During the early phases of the infall, gas can be found in inclined extended and rather thin disc-like structures, and in some galaxies they are similar to (nearly-)~polar disc or ring-like structures. We discuss a possible link between the gas infall, AGN activity and the formation of misaligned components. In particular, we suggest that the AGN activity does not cause the counterrotation, although it is efficiently triggered by the retrograde gas infall, and it correlates well with the misaligned component appearance. We also find evidence of the stellar disc heating visible as an increase of the vertical-to-radial velocity dispersion ratio above unity in both co- and counterrotating components, which implies the importance of the kinematical misalignment in shaping the velocity ellipsoids in disc galaxies.
在IllustrisTNG星系的极端运动失调:起源,结构和内部动力学与大规模的逆旋转星系
现代星系形成理论认为,恒星和气体成分之间的错位通常是由外部气体吸积和/或与其他星系的相互作用造成的。运动失调的极端情况是由所谓的具有逆旋转的星系所证明的,它们具有相对于彼此以相反方向旋转的两个不同的组成部分。我们从IllustrisTNG100宇宙学模拟中提供了对具有逆旋转的星系的深入分析。我们已经发现$25$星系在$2\times10^{9}-3\times10^{10}$~\Msun的恒星质量范围内有大量的恒星反向旋转。在我们的样本中,恒星的反向旋转是大约2-8亿年前发生的外部气体下降的结果。注入导致预先存在的气体的初始移除,这些气体被捕获并与注入的成分混合在一起。气体混合物最终进入反向旋转的气体盘。我们发现,大约90%的恒星反向旋转是在原地形成的,在反向旋转的气体中。在下降的早期阶段,气体可以在倾斜的扩展和相当薄的盘状结构中找到,在一些星系中,它们类似于(近)极盘或环状结构。我们讨论了气体流入、AGN活动和失调成分形成之间的可能联系。特别地,我们认为AGN的活动不会引起反旋转,尽管它是由逆行气体降落有效地触发的,并且它与错位成分的外观密切相关。我们还发现了恒星盘加热的证据,在共旋转和反旋转分量中,垂直与径向速度色散比都大于1,这意味着运动失调在形成盘状星系中速度椭球体方面的重要性。
本文章由计算机程序翻译,如有差异,请以英文原文为准。
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