X-ray spectroscopic study for the evolution of hot plasmas in galaxies and clusters of galaxies

本研究的目的是基于主要来自ASCA的x射线光谱观测，了解椭圆星系和星系团中热气体的形成和演化过程，并为包括ASTRO-E在内的新x射线任务开发能量分辨率优于10 eV的x射线探测器。由于等离子体过程与x射线光谱数据的密切联系，也进行了等离子体过程的理论研究。个人研究领域的主要成果总结如下：ASCA观测：获得了附近明亮星团的温度和金属丰度的空间分布。大尺度的丰度梯度表明星系中产生了金属，而星团外围的热区表明最近发生了与亚星团的合并。确定椭圆星系的金属丰度约为太阳的1倍，并在明亮星系周围发现了极大扩展的x射线辐射。理论研究：研究了Fe-L发射过程，丰度测定存在30%的不确定度。详细研究了复合等离子体的发射过程，并比较了它们与碰撞电离等离子体的光谱差异。硬件开发：对ASTRO-E星载微热计进行了校准，并对探测器的各种特性进行了检查，并将其纳入响应函数。为未来的x射线任务开发了过渡边缘传感器。研究了Mo-Au双分子层的热性能，研制了一种用稀释制冷机冷却的SQUID信号读出系统。

The purpose of this research was to understand the formation and evolution process of hot gas in elliptical galaxies and in clusters of galaxies based on X-ray spectroscopic observations mainly from ASCA, and also to develop X-ray detectors with an energy resolution better than 10 eV for new X-ray mission including ASTRO-E. Theoretical study of the plasma processes was also carried out because of its close connection in understanding the X-ray spectral data. Main achievements in the individual research area are summarized as follows.1. ASCA observations: Spatial distributions of temperature and metal abundance were obtained for near-by bright clusters. Large scale abundance gradient indicated metal production in galaxies, and presence of hot regions in the clusters outskirts showed recent occurrence of mergers with subclusters. Metallicity in elliptical galaxies were determined to be about 1 solar, and greatly extended X-ray emission was discovered around bright galaxies.2. Theoretical study: Fe-L emission process has been examined and there exists and uncertainty of 30% in the abundance determination. Emission process from recombining plasmas were studied in detail and spectral difference from collisionally ionizing plasmas were compared.3. Hardware development: Calibrations of microcalorimeters on-board ASTRO-E were carried out and various detector properties were examined and included in the response function. Development of transition edge sensors for a future X-ray mission was carried out. Thermal properties of Mo-Au bilayers were studied, and a readout system of SQUID signals cooled in a dilution refrigerator has been developed.