标题： X射线从模拟盘星系晕中的发射 显示英文标题

标题： X-ray Emission from Haloes of Simulated Disc Galaxies

摘要： 热气体晕在红移z=0时的光度和0.2-2 keV X射线光度已被计算出来。TreeSPH模拟是完全宇宙学的，44个盘状星系的样本在特征圆周速度V_c = 130-325 km/s范围内变化。这些星系是在具有相当大物理参数范围的模拟中获得的，改变重子分数、气体金属丰度、宇宙紫外线场、宇宙学、暗物质类型以及数值分辨率。这些模型与目前可用的（少量）相关X射线观测结果一致。晕中的热气体量也与银河系脉冲星色散测量的约束一致。即将进行的XMM和钱德拉观测应该能够进行更严格的测试，并对物理参数提供约束。我们发现，相对于这里提出的模型，简单的冷却流模型在高（但仍现实的）冷却效率下会高估X射线光度多达两个数量级。我们的结果显示出一个明显的趋势，即增加冷却效率会导致z=0时X射线光度减少。原因是增加的冷却效率导致了当前在电晕半径内相对于总重子质量的热气体比例减少。在气体金属丰度为三分之一太阳值时，这个热气体比例可以低至几个百分比。我们还发现，大部分X射线辐射来自热星系晕的内部区域（内部约20 kpc）。最后，我们发现对于物理参数的现实选择，盘状星系晕在z=1时的软X射线辐射亮度可能比现在高出一个数量级以上。 显示英文摘要

摘要： Bolometric and 0.2-2 keV X-ray luminosities of the hot gas haloes of simulated disc galaxies have been calculated at redshift z=0. The TreeSPH simulations are fully cosmological and the sample of 44 disc galaxies span a range in characteristic circular speeds of V_c = 130-325 km/s. The galaxies have been obtained in simulations with a considerable range of physical parameters, varying the baryonic fraction, the gas metallicity, the meta-galactic UV field, the cosmology, the dark matter type, and also the numerical resolution. The models are found to be in agreement with the (few) relevant X-ray observations available at present. The amount of hot gas in the haloes is also consistent with constraints from pulsar dispersion measures in the Milky Way. Forthcoming XMM and Chandra observations should enable much more stringent tests and provide constraints on the physical parameters. We find that simple cooling flow models over-predict X-ray luminosities by up to two orders of magnitude for high (but still realistic) cooling efficiencies relative to the models presented here. Our results display a clear trend that increasing cooling efficiency leads to decreasing X-ray luminosities at z=0. The reason is found to be that increased cooling efficiency leads to a decreased fraction of hot gas relative to total baryonic mass inside of the virial radius at present. At gas metal abundances of a third solar this hot gas fraction becomes as low as just a few percent. We also find that most of the X-ray emission comes from the inner parts (inner about 20 kpc) of the hot galactic haloes. Finally, we find for realistic choices of the physical parameters that disc galaxy haloes possibly were more than one order of magnitude brighter in soft X-ray emission at z=1, than at present.