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CONSTRAINTS ON JET-DRIVEN DISK ACCRETION IN SAGITTARIUS A

机译:射手鱼A盘驱动盘吸积的约束

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摘要

We revisit theoretical and observational constraints on geometrically thin disk accretion in Sagittarius A~* (Sgr A~*). We show that the combined effects of mass outflows and electron energization in the hot part of the accretion flow can deflate the inflowing gas from a geometrically thick structure. This allows the gas to cool and even thermalize on an inflow timescale. As a result, a compact, relatively cool disk may form at small radii. We show that magnetic coupling between the relativistic disk and a steady state jet results in a disk that is less luminous than a standard relativistic disk accreting at the same rate. This relaxes the observational constraints on thin-disk accretion in Sgr A~* (and by implication, other low-luminosity active galactic nuclei [LLAGNs]). We find typical cold gas accretion rates of a few × 10~(-9) solar yr~(-1). We also find that the predicted modified disk emission is compatible with existing near-infrared (NIR) observations of Sgr A~* in its quiescent state, provided that the disk inclination angle is approx> 87° and that the jet extracts more than 75% of the accretion power.
机译:我们重新讨论了射手座A〜*(Sgr A〜*)中几何薄盘积聚的理论和观察约束。我们表明,积聚流中较热部分的质量流出和电子激励的综合作用可以使流入的气体从几何上较厚的结构中逸出。这样可以使气体在流入时间范围内冷却甚至热化。结果,可以以较小的半径形成紧凑的,相对凉爽的盘。我们表明,相对论磁盘和稳态射流之间的磁耦合导致磁盘的发光程度低于以相同速率吸积的标准相对论磁盘。这放宽了Sgr A〜*中薄盘积聚的观测限制(并暗示其他低发光活性银河核[LLAGNs])。我们发现典型的冷气积聚速率为几个×10〜(-9)太阳yr〜(-1)。我们还发现,预测的修正盘发射与静止状态下Sgr A〜*的现有近红外(NIR)观测值兼容,前提是盘倾角大约大于87°,并且射流提取率超过75%的积聚力。

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