Is There Still Room for Warm/Hot Gas? Simulating the X-Ray Background Spectrum
Is There Still Room for Warm/Hot Gas? Simulating the X-Ray Background Spectrum
复制标题
还有温/热气体的空间吗？
DOI：
--
复制
发表时间：
2000
期刊：
影响因子：
--
通讯作者：
R. Cen
中科院分区：
文献类型：
--
作者：
L. A. Phillips;J. Ostriker;R. Cen
在低的红移，重子在所有已知的水库人口普查福尔斯了2-4倍，低于总重子密度预测从大爆炸核合成参数和观察到的轻元素比。最近的宇宙学流体动力学模拟表明，这些失踪的重子的一个显着的部分可能是在温暖/热星系际介质（WHIM）中的灯丝和晕，其中大多数场星系嵌入。随着钱德拉的源计数结果的发布和最近在O VI类星体吸收线中对这种气体的探测，研究X射线背景（XRB）的预测和限制变得很有趣。我们已经使用了新的流体动力学模拟预测总的X射线光谱从星系际介质和WHIM单独在100 eV-10 keV的范围。我们发现，当考虑到观测到的XRB的归一化和ΩB值的不确定性时，我们的结果与目前对WHIM对XRB的贡献的观测限制是一致的。在0.5-2 keV的范围内，我们预计这一分量的贡献为0.24 × 10-12 ergs-1 cm-2 deg-2，即河外表面亮度的5%-15%。峰值部分发生在0.5-0.8千电子伏的范围内，其中预测的线发射反映了在最新的ASCA/ROSAT XRB数据中看到的光谱凸起。
At low redshifts, a census of the baryons in all known reservoirs falls a factor of 2-4 below the total baryon density predicted from big bang nucleosynthesis arguments and observed light-element ratios. Recent cosmological hydrodynamic simulations suggest that a significant fraction of these missing baryons could be in the warm/hot intergalactic medium (WHIM) in the filaments and halos within which most field galaxies are embedded. With the release of source count results from Chandra and recent detections of this gas in O VI quasar absorption lines, it becomes interesting to examine the predictions and limits placed on this component of the X-ray background (XRB). We have used new hydrodynamical simulations to predict the total X-ray spectrum from the intergalactic medium and the WHIM alone in the 100 eV-10 keV range. We find that, when uncertainties in the normalization of the observed XRB and the value of Ωb are taken into account, our results are consistent with current observational limits placed on the contribution of emission from the WHIM to the XRB. In the 0.5-2 keV range, we expect the contribution from this component to be 0.24 × 10-12 ergs s-1 cm-2 deg-2 or between 5% and 15% of the extragalactic surface brightness. The peak fraction occurs in the 0.5-0.8 keV range where the predicted line emission mirrors a spectral bump seen in the latest ASCA/ROSAT XRB data.