标题： 光电离与矮星系的形成 显示英文标题

标题： Photoionization and the Formation of Dwarf Galaxies

摘要： 有人认为紫外光致电离背景辐射场会抑制矮星系的形成，甚至可能阻碍较大星系的形成。为了检验这一点，我们提出了在宇宙学冷暗物质（CDM）背景下，有无光致电离背景的小天体形成气体动力学模拟。这些天体是从红移为2.4处的一个无碰撞模拟中选出，并以更高的分辨率重新运行，包括气体动力学效应和使用分层粒子网格。模拟了五个圆周速度为46公里/秒的天体。光致电离背景的存在对这些天体中坍缩气体的数量影响很小，最多减少30%的冷坍缩气体量。高分辨率模拟中发现的小型天体分析表明，光致电离背景仅显著影响那些具有小于10^9太阳质量的引力稳定晕质量和小于23公里/秒的圆周速度的天体的形成。然而，背景辐射场极大地改变了电离平衡。当包含光致电离背景时，穿过这些天体的典型视线的中性氢柱密度减少了四个数量级。 显示英文摘要

摘要： It has been argued that a UV photoionizing background radiation field suppresses the formation of dwarf galaxies, and may even inhibit the formation of larger galaxies. In order to test this, we present gas-dynamical simulations of the formation of small objects in a CDM universe with and without a photoionizing background. The objects are selected from a collisionless simulation at a redshift of 2.4, and rerun at higher resolution including the effects of gas dynamics and using a hierarchical grid of particles. Five objects, each with a circular speed of 46 km/sec are simulated. The presence of the photoionizing background has only a small effect on the amount of gas that collapses in these objects, reducing the amount of cold collapsed gas by at most 30%. Analysis of the smaller objects found in the higher resolution simulation indicates that the photoionizing background only significantly affects the formation of objects with a virialized halo mass less than 10^9 soalr masses and circular speeds less than 23 km/sec. However, the ionization balance is greatly changed by the presence of the background radiation field. Typical lines of sight through the objects have 4 orders of magnitude less neutral hydrogen column density when the photoionizing background is included.