Where Are the Baryons?
Where Are the Baryons?
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DOI：
10.1086/306949
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发表时间：
1998-06
期刊：
影响因子：
--
通讯作者：
R. Cen;J. Ostriker
中科院分区：
文献类型：
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作者：
R. Cen;J. Ostriker
新的高分辨率，大尺度宇宙流体动力学星系形成模拟的标准冷暗物质模型（与宇宙常数）被用来预测重子在当前和中等红移的分布。发现重子的平均温度是时间的递增函数，目前大多数重子的平均温度在105 ~ 107 K之间。因此，不仅宇宙由暗物质主导，而且还有一半以上的正常物质尚未被探测到。探测这种暖/热气体带来了观测上的挑战，这需要灵敏的EUV和x射线卫星。特征包括软宇宙x射线背景，由于团内和团间的固有温暖气体沿视线投射到团上，热星团中的明显温暖成分，x射线和紫外类星体光谱中的吸收谱线[例如，O VI (1032, 1038) a谱线，O VII 574 eV谱线]，强发射谱线（例如，O VIII 653 eV谱线），以及低红移，宽，低柱密度的Lyα吸收谱线。我们估计大约四分之一的河外软x射线背景（0.7 keV）来自热/热气体，其中一半来自z<0.65，四分之三来自z<1.00，因此在深光学图像上应该可以识别出源区域。
New high-resolution, large-scale cosmological hydrodynamic galaxy formation simulations of a standard cold dark matter model (with a cosmological constant) are utilized to predict the distribution of baryons at the present and at moderate redshift. It is found that the average temperature of baryons is an increasing function of time, with most of the baryons at the present time having a temperature in the range of 105-107 K. Thus not only is the universe dominated by dark matter, but more than one-half of the normal matter is yet to be detected. Detection of this warm/hot gas poses an observational challenge, which requires sensitive EUV and X-ray satellites. Signatures include a soft cosmic X-ray background, apparent warm components in hot clusters due to both intrinsic warm intracluster and intercluster gas projected onto clusters along the line of sight, absorption lines in X-ray and UV quasar spectra [e.g., O VI (1032, 1038) A lines, O VII 574 eV line], strong emission lines (e.g., O VIII 653 eV line), and low-redshift, broad, low column density Lyα absorption lines. We estimate that approximately one-fourth of the extragalactic soft X-ray background (at 0.7 keV) arises from the warm/hot gas, half of it coming from z<0.65, and three-quarters coming from z<1.00, so the source regions should be identifiable on deep optical images.