测量盘星系中的径向流

中文摘要 AI 辅助

大量理论研究表明，宇宙时间内，从星系际介质吸积的气体对维持星系的恒星形成至关重要，但由于缺乏直接证据，气体吸积的机制仍知之甚少。在一些模型中，气体吸积被认为发生在星系的外盘，随后需通过径向流将其转移到内部恒星形成盘，因此，寻找并量化这类径向流为推断吸积气体的详细性质提供了可能。然而，由于径向速度与旋转速度之间存在巨大差异，检测径向流极具挑战性；此外，这类流产生的速度场畸变类似翘曲结构的效应，进一步增加了量化难度。为解决该问题，我们开发了一种测量盘星系轴对称径向速度的新方法，基于三维运动学拟合软件\texttt{$^{\rm 3D}$Barolo}，设计了专门的工作流程以测量盘星系中的轴对称径向运动，并通过自举法获得可靠的不确定性估计。我们利用真实的轴对称 mock 星系以及从 TNG50 流体动力学模拟中抽取的一小类“观测到的”类银河系样本验证了该方法，测试表明，我们的方法效果良好，能够克服径向运动与翘曲之间的简并性。我们分析的 TNG50 星系在其盘的大部分区域存在非轴对称的流入和流出，但平均而言，未表现出相干径向流的全局趋势。

英文摘要

Numerous theoretical studies suggest that gas accretion from the intergalactic medium is essential to feed star formation in galaxies throughout cosmic time. However, the mechanism of gas accretion remains poorly understood, as direct evidence is lacking. In some models, gas accretion is expected to take place in the outer discs of galaxies, from where it should be transferred to the inner star-forming discs through radial flows. Finding such flows and quantifying them, therefore, opens the possibility of inferring the detailed properties of the accreting gas. Unfortunately, detecting radial flows is challenging due to the large disparity between radial and rotational velocities. Additionally, the distortions in velocity fields produced by these flows resemble the effects of warped structures, further complicating their quantification. To address this, we have developed a new methodology to measure axisymmetric radial velocities in disc galaxies. Relying on the 3D kinematic fitting software \texttt{$^{\rm 3D}$Barolo}, we have designed a dedicated workflow to measure axisymmetric radial motions in disc galaxies and to obtain robust uncertainty estimates through a bootstrapping approach. We validated this approach using realistic axisymmetric mock galaxies as well as a small sample of `observed' Milky Way-like galaxies drawn from the TNG50 hydrodynamic simulation. These tests demonstrate that our method works well and is capable of overcoming the degeneracy between radial motions and warps. The TNG50 galaxies we analysed have large regions in their discs with non-axisymmetric inflows and outflows, but they show, on average, no global trend of coherent radial flows.

发表机构

• Kapteyn Astronomical Institute, University of Groningen（格罗宁根大学卡佩恩天文研究所）
• Leiden Observatory, Leiden University（莱顿大学莱顿天文台）
• Università di Firenze, Dipartimento di Fisica e Astronomia（佛罗伦萨大学物理与天文学系）
• INAF - Osservatorio Astrofisico di Arcetri（意大利国家天体物理研究所阿切特里天文观测站）

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