标题： 斯特姆gren球体的弥散性质 显示英文标题

标题： The Diffuse Nature of Stromgren Spheres

摘要： 在本快报中，我们论证了HII区性质的标准解析推导（例如，电离前锋的速度、形状和渐近位置）需要更精确的处理。 这些推导使用了就地近似法，实际上忽略了辐射场的弥散分量。 我们证明了事实上HII区是以扩散为主的。 这导致了不均匀HII区的形态会有显著差异，因为阴影效应对表观形状的影响较弱。 此外，它还将影响电离前锋的传播速度。 我们通过解析推导HII区内部辐射结构来量化我们的论点，充分考虑了几种不同的宇宙学相关的密度分布下的扩散效应。 显示英文摘要

摘要： In this Letter, we argue that the standard analytical derivations of properties of HII regions, such as the speed, shape and asymptotic position of ionisation fronts require a more precise treatment. These derivations use the on the spot approximation, which in effect ignores the diffuse component of the radiation field. We show that, in fact, HII regions are diffusion dominated. This has as a result that the morphology of inhomogeneous HII regions will be drastically different, because shadowing effects have a less profound impact on the apparent shape. Moreover, it will have influence on the propagation speed of ionisation fronts. We quantify our claims by analytically deriving the internal radiation structure of HII regions, taking diffusion fully into account for several different cosmologically relevant density distributions.