Early Evolution of Spin Direction in Dark Matter Halos and the Effect of the Surrounding Large-scale Tidal Field* * Thesis work conducted at Facultad de Matemática, Astronomía, Física y Computación, Universidad Nacional de Córdoba, Córdoba, Argentina. † † PhD Thesis directed by Manuel Merchán; PhD Degree awarded 2023 July 31.
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引用次数: 0
Abstract
It is usually assumed that the angular momentum (AM) of dark matter halos arises during the linear stages of structure formation, as a consequence of the coupling between the proto-haloes’ shape and the tidal field produced by their surrounding density perturbations. This approach, known as linear tidal torque theory (TTT), has been shown to make fairly good predictions about the mean evolution of both the AM amplitude and orientation up to approximately the time when the proto-haloes collapse. After this point, proto-haloes are increasingly affected by nonlinear processes that are not taken into account by the model. However, it has been seen in numerical simulations that, even at very early stages, the AM of proto-haloes is systematically reoriented toward perpendicularity with respect to the forming cosmic filaments, in contradiction with the fixed direction expected from the TTT. In this work we present a novel analytical approach that introduces an anisotropic scaling factor to the standard TTT equations, which allows the AM orientation to change in time, even during the linear regime. The amplitude and direction of this shift depend on the large scale tidal field around the forming proto-haloes. Our results significantly improve the predictions for the AM direction up to the time of protohalo collapse and, in some cases, even further in time.
通常的假设是,暗物质光环的角动量(AM)产生于结构形成的线性阶段,是原光环的形状与其周围密度扰动所产生的潮汐场之间耦合的结果。这种方法被称为线性潮汐力矩理论(TTT),已被证明可以很好地预测 AM 振幅和方向的平均演化,直至原初光环坍缩为止。在此之后,原螺旋会越来越多地受到非线性过程的影响,而这些过程并没有被模型考虑在内。然而,我们在数值模拟中发现,即使在很早的阶段,原恒星的AM方向也会系统地调整为与正在形成的宇宙丝垂直,这与TTT所预期的固定方向是矛盾的。在这项工作中,我们提出了一种新颖的分析方法,即在标准 TTT 方程中引入各向异性的缩放因子,从而使 AM 方向随时间发生变化,即使在线性状态下也是如此。这种变化的幅度和方向取决于正在形成的原海泡石周围的大尺度潮汐场。我们的结果极大地改进了对 AM 方向的预测,直至原光环坍缩之时,在某些情况下,甚至在时间上更进一步。
期刊介绍:
The Publications of the Astronomical Society of the Pacific (PASP), the technical journal of the Astronomical Society of the Pacific (ASP), has been published regularly since 1889, and is an integral part of the ASP''s mission to advance the science of astronomy and disseminate astronomical information. The journal provides an outlet for astronomical results of a scientific nature and serves to keep readers in touch with current astronomical research. It contains refereed research and instrumentation articles, invited and contributed reviews, tutorials, and dissertation summaries.