标题： 星形成区域中相空间密度的演化 显示英文标题

标题： The evolution of phase space densities in star-forming regions

摘要： 多维相空间密度（包括位置和速度）的恒星形成区域可能包含关于恒星和行星形成初始条件的信息。 最近，一种基于马氏距离的新度量被用来表明，热木星更可能存在于高6D相空间密度的系外行星宿主恒星周围，这表明这些行星的形成环境更加动态。 然而，后续的研究表明，这一初步结果可能是由于热木星的年龄偏差及其宿主恒星的动力学特性造成的。 我们通过将其应用于具有不同形态的静态区域（无论是亚结构还是平滑且中心集中）来测试马氏距离和密度区分不同恒星形成区域的能力。 我们发现，马氏距离无法区分不同的形态，并且仅使用马氏距离或密度无法约束N体模拟的初始条件。 此外，我们发现相空间中的维度越多，马氏密度在区分不同初始条件方面的效果就越差。 我们表明，一个区域的平均三维（x，y，z）马氏密度和Q参数的组合可以约束其初始维里状态。 然而，这是由于Q参数的辨别能力，而不是由于马氏密度中印有额外的信息。 因此，我们建议继续使用多种诊断方法来确定恒星形成区域的初始条件，而不是依赖单一的多维度量。 显示英文摘要

摘要： The multi-dimensional phase space density (both position and velocity) of star-forming regions may encode information on the initial conditions of star and planet formation. Recently, a new metric based on the Mahalanobis distance has been used to show that hot Jupiters are more likely to be found around exoplanet host-stars in high 6D phase space density, suggesting a more dynamic formation environment for these planets. However, later work showed that this initial result may be due to a bias in the age of hot Jupiters and the kinematics of their host stars. We test the ability of the Mahalanobis distance and density to differentiate more generally between star-forming regions with different morphologies by applying it to static regions that are either substructured or smooth and centrally concentrated. We find that the Mahalanobis distance is unable to distinguish between different morphologies, and that the initial conditions of the N-body simulations cannot be constrained using only the Mahalanobis distance or density. Furthermore, we find that the more dimensions in the phase space the less effective the Mahalanobis density is at distinguishing between different initial conditions. We show that a combination of the mean three-dimensional (x, y, z) Mahalanobis density and the Q-parameter for a region can constrain its initial virial state. However this is due to the discriminatory power of the Q-parameter and not from any extra information imprinted in the Mahalanobis density. We therefore recommend continued use of multiple diagnostics for determining the initial conditions of star-forming regions, rather than relying on a single multi-dimensional metric.