整个银河系的稳态核合成
Steady-state nucleosynthesis throughout the Galaxy
摘要：
对核合成产生的特征伽马射线谱线进行测量和天体物理学解释是INTEGRAL飞行任务，特别是其光谱仪SPI的突出科学目标之一。从26铝和60铁衰变线的排放来源于积累的喷出物的核合成源，并出现扩散的性质。26 Al和60 Fe被认为主要来自大质量星团。伽马射线观测打开了一扇有趣的窗口，可以追踪核合成喷出物的命运和流动，在它们离开直接来源和它们的诞生地之后，以及在它们与周围星际气体混合的路径上。INTEGRAL 26 Al发射图像证实了早期发现的团块和整个银河系平面的范围，支持其起源于恒星群。积分光谱学解决了这条线，并发现了多普勒加宽和大规模星系旋转的系统位移。但是~200 km/s的额外速度表明，26 Al优先在螺旋臂之间向前延伸的大型超级气泡内衰变。附近猎户座和波江座超级气泡的26 Al线发射的检测支持了这一解释。来自26 Al和其他核合成喷出物的β +衰变的正电子被发现不能解释INTEGRAL测量到的511 keV正电子湮灭γ射线的形态。INTEGRAL测量的60 Fe信号是弥散的，但对于成像解释来说太弱，排除了点状/集中源的起源。60 Fe/26 Al比率被限制在0.2-0.4的范围内。除了提高这些结果的精度，来自新星（通过22 Na放射性）和来自我们银河系过去中子星合并（来自r过程放射性）的扩散核合成贡献是剩余任务扩展的令人兴奋的新前景。
英文摘要：
Measurement and astrophysical interpretation of characteristic gamma-ray lines from nucleosynthesis was one of the prominent science goals of the INTEGRAL mission and in particular its spectrometer SPI. Emission from 26Al and from 60Fe decay lines originates from accumulated ejecta of nucleosynthesis sources, and appears diffuse in nature. 26Al and 60Fe are believed to originate mostly from massive star clusters. Gamma-ray observations open an interesting window to trace the fate and flow of nucleosynthesis ejecta, after they have left the immediate sources and their birth sites, and on their path to mix with ambient interstellar gas. The INTEGRAL 26Al emission image confirms earlier findings of clumpiness and an extent along the entire plane of the Galaxy, supporting its origin from massive-star groups. INTEGRAL spectroscopy resolved the line and found Doppler broadenings and systematic shifts from large-scale galactic rotation. But an excess velocity of ~200 km/s suggests that 26Al decays preferentially within large superbubbles that extend in forward directions between spiral arms. The detection of 26Al line emission from nearby Orion and the Eridanus superbubble supports this interpretation. Positrons from beta+ decays of 26Al and other nucleosynthesis ejecta have been found to not explain the morphology of positron annihilation gamma-rays at 511 keV that have been measured by INTEGRAL. The 60Fe signal measured by INTEGRAL is diffuse but too weak for an imaging interpretation, an origin from point-like/concentrated sources is excluded. The 60Fe/26Al ratio is constrained to a range 0.2-0.4. Beyond improving precision of these results, diffuse nucleosynthesis contributions from novae (through 22Na radioactivity) and from past neutron star mergers in our Galaxy (from r-process radioactivity) are exciting new prospects for the remaining mission extensions.
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