Detection of a Drag Force in G2's Orbit: Measuring the Density of the Accretion Flow onto Sgr A* at 1000 Schwarzschild Radii
Detection of a Drag Force in G2's Orbit: Measuring the Density of the Accretion Flow onto Sgr A* at 1000 Schwarzschild Radii
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DOI：
10.3847/1538-4357/aaf4f8
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发表时间：
2018-12
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通讯作者：
S. Gillessen;P. Plewa;F. Widmann;S. Fellenberg;M. Schartmann;M. Habibi;A. Rosales;M. Bauböck;J. Dexter;F. Gao;I. Waisberg;F. Eisenhauer;O. Pfuhl;T. Ott;A. Burkert;P. D. Zeeuw;P. D. Zeeuw;R. Genzel;R. Genzel
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作者：
S. Gillessen;P. Plewa;F. Widmann;S. Fellenberg;M. Schartmann;M. Habibi;A. Rosales;M. Bauböck;J. Dexter;F. Gao;I. Waisberg;F. Eisenhauer;O. Pfuhl;T. Ott;A. Burkert;P. D. Zeeuw;P. D. Zeeuw;R. Genzel;R. Genzel
银河系中心黑洞SgrA*是进食不足的大质量黑洞的典型例子。极低的吸积率可以用辐射效率低的吸积流模型来解释。由于缺乏合适的探测器，测试这些型号被证明是困难的。无线电和亚毫米偏振测量将气流限制在非常接近事件视界的位置。解析邦迪半径的X射线观测给出了大约更远的四个数量级的估计。在这里，我们提出了一种新的，间接测量吸积流密度的中间半径。我们使用气云G2的动力学来探测周围的密度。我们检测到阻力的存在使G2减速，其统计意义为≈9σ。在约1000Schwarzschild半径处探测吸积流密度，得到数密度为≈4×103 cm−3。自相似吸积模型的密度在内区和邦迪半径之间遵循幂函数径向分布，其预测值与此相似。
The Galactic Center black hole Sgr A* is the archetypical example of an underfed massive black hole. The extremely low accretion rate can be understood in radiatively inefficient accretion flow models. Testing those models has proven to be difficult due to the lack of suitable probes. Radio and submillimeter polarization measurements constrain the flow very close to the event horizon. X-ray observations resolving the Bondi radius yield an estimate roughly four orders of magnitude further out. Here, we present a new, indirect measurement of the accretion flow density at intermediate radii. We use the dynamics of the gas cloud G2 to probe the ambient density. We detect the presence of a drag force slowing down G2 with a statistical significance of ≈9σ. This probes the accretion flow density at around 1000 Schwarzschild radii and yields a number density of ≈4 × 103 cm−3. Self-similar accretion models where the density follows a power-law radial profile between the inner zone and the Bondi radius have predicted similar values.