Observational Study of the Cosmic X-ray Background with the Scientifica Satellite ASTRO-D

这项科学计划的目标是利用1993年2月20日发射的科学卫星ASTRO-D(ASCA)调查宇宙X射线背景(CXB)，并对ASCA上的气体成像光谱仪(GIS)进行在轨定标。CXB是一种已知的神秘现象，它是X射线天文学诞生之初的科学现象，但其确切来源尚不清楚。经过三年的调研，取得了以下成果：1.完成了对地理信息系统的在轨性能验证和详细标定。特别是，已经准确地量化了地理信息系统的颗粒背景，这对于包括CXB在内的漫反射排放的调查是重要的。通过考虑X射线望远镜的点扩散函数和杂散光，提出了一种新的数据分析方案，并将其应用于广泛扩展的X射线源。特别是：(1)揭示了大尺度磁场的重要性；(2)暗物质的分布表现出星系/星系团的层次结构；(3)在附近的正常星系中发现了一些低光度的活动核。CXB谱在1-10keV的能量范围内呈现单次幂函数形状，光子指数为1.4。这与以前用ROSAT卫星获得的结果相矛盾。此外，在剔除大于3*10^-13&gt；erg/S/cm^2(在2-10keV)的点源后，证实了TE CXB表面亮度的场场起伏最大为&lt；正负&gt；3%。这些结果给那些试图将CXB合成为远处物体的叠加的模型提供了强烈的约束。

The objective of this scientific project is to investigate the cosmic X-ray background (CXB), using the scientific satellite ASTRO-D (ASCA) launched on 1993 February 20, and to carry out in-orbit calibration of the GIS (Gas Imaging Spectrometer) instrument onboard ASCA.The CXB is anenigmatic phenomenon known science the birth of the X-ray astronomy, but its exact origin is still unknown. Through three years of investigation, the following achievements have been obtained.1. The in-orbit performance verification and detailed calibration of the GIS have been accomplished. In particular, the GIS particle background has been precisely quantified, which is important for the investigation of diffuse emissions including the CXB.2. By taking into account the point spread function and stray light of the X-ray telescope, a new scheme of data analysis has been developed for application to widely extended X-ray sources.3. New insight has been obtained for various extra-Galactic objects which potentially contribute to the CXB.In particular ; (1) importance of the large-scale magnetic fields has been revealed ; (2) the dark matter distribution has been found to exhibit galaxy/cluster tierarchy ; and (3) a number of low-luminosity active nuclei have been discovered in nearby normal galaxies.4. The CXB spectrum has been show to exhibit a single power-law shape with a photon index 1.4 over the 1-10 keV energy range. This contradicts the previous results obtained with the ROSAT satellite. In addition, after removing point sources brighter than 3*10^<-13> erg/s/cm^2 (in 2-10 keV), the field-to field fluctuation of te CXB surface brightness is confirmed to be <plus-minus>3% at most. These results give strong constraints to the models that attempt to synthesize the CXB as a superposition of distant objects.