预处理、群吸积和伴生晕的轨道
Pre-processing, group accretion and the orbital trajectories of associated subhaloes
摘要：
我们使用一个高分辨率的宇宙学暗物质的模拟研究孤立的主机周围的晕和subhaloes的轨道轨迹。我们仔细地记录所有的拱点，并利用它们来区分第一次坠落的晕和那些占据更进化轨道的晕。我们发现，大约有21%的subhaloes在主机的维里半径目前的第一次下降，还没有达到他们的第一个轨道近心点;大约44%的仍在接近他们的第一个远心点后，下降。对于所研究的宿主质量范围，大约有一半的吸积系统在下落前进行了预处理，约20%是成组吸积的。我们确认，整个人口的吸积subhaloes -通常被称为“相关”subhaloes -远远超出其主机的维里半径，目前大约有一半居住在距离超过$\approx 1.2\times r_{200}$。这些后溅晕中的许多在进入后获得了轨道能量，并占据了极端的轨道，使它们远远超过了最初的转向半径。这种极端的轨道是在松散结合的群体的初始吸积和溶解过程中产生的，但也是通过随后轨道上的subhalo之间的穿透相遇而产生的。同样的过程也可能引起轨道能量的意外突然损失。这些影响结合起来，引起了一个很大的变化，在比率的吸积系统的apocentres。我们发现，在2维里半径从主机中心，第一次降落晕的浓度是非常相似的孤立场晕，而后溅晕，以及系统的预处理，是相当多的集中。
英文摘要：
We use a high-resolution cosmological dark matter-only simulation to study the orbital trajectories of haloes and subhaloes in the environs of isolated hosts. We carefully tally all apsis points and use them to distinguish haloes that are infalling for the first time from those that occupy more evolved orbits. We find that roughly 21 per cent of subhaloes within a host's virial radius are currently on first infall, and have not yet reached their first orbital pericentre; roughly 44 per cent are still approaching their first apocentre after infall. For the range of host masses studied, roughly half of all accreted systems were pre-processed prior to infall, and about 20 per cent were accreted in groups. We confirm that the entire population of accreted subhaloes -- often referred to as "associated" subhaloes -- extend far beyond the virial radii of their hosts, with roughly half currently residing at distances that exceed $\approx 1.2\times r_{200}$. Many of these backsplash haloes have gained orbital energy since infall, and occupy extreme orbits that carry them well past their initial turnaround radii. Such extreme orbits are created during the initial accretion and dissolution of loosely bound groups, but also through penetrating encounters between subhaloes on subsequent orbits. The same processes may also give rise to unexpectedly abrupt losses of orbital energy. These effects combine, giving rise to a large variation in the ratio of sequent apocentres for accreted systems. We find that, within 2 virial radii from host centres, the concentrations of first-infall halos are remarkably similar those of isolated field halos, whereas backsplash haloes, as well as systems that were pre-processed, are considerably more concentrated.
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