论文标题
光环密度梯度曲线的各向异性和特征尺度
Anisotropy and characteristic scales in halo density gradient profiles
论文作者
论文摘要
我们使用大型的N体模拟来研究光环和周围密度梯度轮廓的特征量表，质量从$ 10^{12} $到$ 10^{15} {15} h^{ - 1} {\ rm m_ \ odot} $。我们沿着局部潮汐张量的主要（T_1）和小（T_3）轴分别研究了曲线，以及特征尺度如何依赖于光晕质量，形成时间和环境。我们在梯度剖面中发现了两种突出的特征，一个深的“山谷”和一个突出的“峰”。我们使用高斯工艺回归来符合梯度剖面并识别局部极值以确定与这些特征相关的量表。在山谷周围，我们确定了三种不同类型的不同局部最小值，对应于围绕光晕的颗粒的苛性遗传。三种苛性碱的外观和深度显着取决于局部潮汐场定义的方向，晕孔的形成时间和环境。第一个苛性碱位于半径为r> 0.8R_ {200}，与Splashback特征相对应，在输入后的第一个apocenter处由粒子支配。第二和第三个苛性碱，分别为0.6R_ {200}和0.4R_ {200}，只能可靠地确定旧的晕孔。第一个苛性碱始终是T_3沿T_3的最突出特征，但在T_1或方位角平均的轮廓中可能并非如此，这表明在使用平均配置文件研究飞溅半径时必须谨慎行事。我们发现，当第一和其他苛性碱之间进行适当的分离时，Splashback功能大约是各向同性的。我们还在密度梯度配置文件中确定位于$ \ sim $ 2.5R_ {200}的峰值功能。此功能是沿T_1的最突出的功能，是由光环外部结构的质量积累产生的。我们还讨论了这些特征的起源及其观察意义。
We use a large N-body simulation to study the characteristic scales in the density gradient profiles in and around halos with masses ranging from $10^{12}$ to $10^{15} h^{-1}{\rm M_\odot}$. We investigate the profiles separately along the major (T_1) and minor (T_3) axes of the local tidal tensor and how the characteristic scales depend on halo mass, formation time, and environment. We find two kinds of prominent characteristic features in the gradient profiles, a deep `valley' and a prominent `peak'. We use the Gaussian Process Regression to fit the gradient profiles and identify the local extrema to determine the scales associate with these features. Around the valley, we identify three types of distinct local minima, corresponding to caustics of particles orbiting around halos. The appearance and depth of the three caustics depend significantly on the direction defined by the local tidal field, formation time and environment of halos. The first caustic is located at a radius r>0.8R_{200}, corresponding to the splashback feature, and is dominated by particles at their first apocenter after infall. The second and third caustics, around 0.6R_{200} and 0.4R_{200} respectively, can be determined reliably only for old halos. The first caustic is always the most prominent feature along T_3, but may not be the case along T_1 or in azimuthally-averaged profiles, suggesting that caution must be taken when using averaged profiles to investigate the splashback radius. We find that the splashback feature is approximately isotropic when proper separations are made between the first and the other caustics. We also identify a peak feature located at $\sim$ 2.5R_{200} in the density gradient profile. This feature is the most prominent along T_1 and is produced by mass accumulations from the structure outside halos. We also discuss the origins of these features and their observational implications.
