Search for dark baryon in the universe using oxygen emission lines in soft X-ray band

1)我们和我们的德国合作者克劳斯·多拉格博士一起开发并运行了一个宇宙水力学代码。该程序考虑了辐射冷却、恒星形成、超新星气体加热、化学演化等多种物理过程。2)利用上述模拟结果，我们建立了一个模拟星系表，并讨论了通过氧发射线探测附近星系团外围的温热星际介质的可行性(Yoshikawa等人)。3)我们还研究了利用背景类星体和伽马射线暴发光后的X射线探测奇想吸收线的可行性(Kawahara等人。4)指出元素丰度不符合电离平衡。我们利用模拟数据跟踪了氧电离态的时间演化，确实表明电离平衡是不成立的。我们发现，不同电离态的氧线强度比是偏离电离平衡的一个很好的指示器(Yoshikawa和Sasaki，2006)。5)我们提出了一个新的星系团内介质温度和密度不均匀的经验分析模型，并表明这很好地解释了钱德拉X射线卫星(Kwahar等人，2007,2008)对A3667星系团的观测数据。

1) We developed and ran a cosmological hydro-code with our German collaborator, Dr. Klaus Dolag. The code takes account of a variety of physical processes including radiative cooling, star formation, gas heating due to supernovae, chemical evolution.2) Using the above simulation results, we constructed a mock galaxy catalog in the Local Universe, and discussed the detection feasibility of WHIM (warm-hot intergalactic medium) associated with outskirts of nearby galaxy clusters via oxygen emission lines (Yoshikawa et al. 2004).3) We also studied the detection feasibility of absorption lines of WHIM using the background quasars and X-ray after glow of gamma-ray bursts (Kawahara et al. 2006).4) It has been pointed out that the element abundance in WHIM does not obey the ionization equilibrium. We followed the time evolution of the oxygen ionization states using the simulation data, and indeed showed that the ionization equilibrium is not valid in WHIM. We found that the intensity ratio of oxygen lines in different ionization states is a good indicator of the departure from the ionization equilibrium (Yoshikawa and Sasaki 2006).5) We proposed a new empirical analytic model for temperature and density inhomogeneities in intra-cluster medium, and showed that this nice explains the observation data of galaxy cluster A3667 from Chandra X-ray satellite (kawahar et al.2007,2008).