PHYSICS OF THE GALACTIC CENTER CLOUD G2, ON ITS WAY TOWARD THE SUPERMASSIVE BLACK HOLE
PHYSICS OF THE GALACTIC CENTER CLOUD G2, ON ITS WAY TOWARD THE SUPERMASSIVE BLACK HOLE
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DOI：
10.1088/0004-637x/750/1/58
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发表时间：
2012-01
期刊：
影响因子：
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通讯作者：
A. Burkert;M. Schartmann;C. Alig;S. Gillessen;R. Genzel;T. Fritz;F. Eisenhauer
中科院分区：
文献类型：
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作者：
A. Burkert;M. Schartmann;C. Alig;S. Gillessen;R. Genzel;T. Fritz;F. Eisenhauer
我们研究了小型气体云 G2 的起源、结构和演化，该气体云的轨道几乎直接进入银河系中心超大质量黑洞 (SMBH)。 G2 是人马座 A* 热吸积带的敏感探测器，需要与捕获的激波加热恒星风模型非常吻合的气体温度和密度。它的质量等于临界质量，低于该质量冷团块将被蒸发迅速破坏。它的质量还受到以下事实的限制：在远心，它的声音穿越时间尺度等于它的落入时间尺度。我们的数值模拟表明，如果 G2 于 1995 年在距离超大黑洞 7.6 × 1016 cm 处与周围环境形成压力平衡，则可以很好地重现所观察到的 G2 结构和演化。如果云团如从轨道上预期的那样在“顺时针”恒星盘的远心处形成，那么到 2011 年它将被撕成一条非常细长的意大利面条状细丝，但这一现象并未被观测到。如果 G2 是在远心处形成的更大的壳状结构的头部，这个问题就可以解决。我们的数值模拟表明，这种情况不仅解释了 G2 观测到的运动学和几何特性，还解释了 Brγ 观测到的尾随云的低表面亮度气体尾部。 2013年，在经过超大质量黑洞时，G2将分裂成一串水滴，这些水滴将在未来30年内与周围的热气体混合并触发活跃的星系核活动周期。
We investigate the origin, structure, and evolution of the small gas cloud G2, which is on an orbit almost straight into the Galactic central supermassive black hole (SMBH). G2 is a sensitive probe of the hot accretion zone of Sgr A*, requiring gas temperatures and densities that agree well with models of captured shock-heated stellar winds. Its mass is equal to the critical mass below which cold clumps would be destroyed quickly by evaporation. Its mass is also constrained by the fact that at apocenter its sound crossing timescale was equal to its infall timescale. Our numerical simulations show that the observed structure and evolution of G2 can be well reproduced if it forms in pressure equilibrium with its surroundings in 1995 at a distance from the SMBH of 7.6 × 1016 cm. If the cloud had formed at apocenter in the “clockwise” stellar disk as expected from its orbit, it would be torn into a very elongated spaghetti-like filament by 2011, which is not observed. This problem can be solved if G2 is the head of a larger, shell-like structure that formed at apocenter. Our numerical simulations show that this scenario explains not only G2's observed kinematical and geometrical properties but also the Brγ observations of a low surface brightness gas tail that trails the cloud. In 2013, while passing the SMBH, G2 will break up into a string of droplets that within the next 30 years will mix with the surrounding hot gas and trigger cycles of active galactic nucleus activity.