The mass of the central black hole in many active galactic nuclei has been estimated on the basis of the assumption that the dynamics of the broad emission line gas are dominated by the gravity of the black hole. The most commonly-employed method is to estimate a characteristic size-scale $r_*$ from reverberation mapping experiments and combine it with a characteristic velocity $v_*$ taken from the line profiles; the inferred mass is then estimated by $r_* v_*^2/G$. We critically discuss the evidence supporting the assumption of gravitational dynamics and find that the arguments are still inconclusive. We then explore the range of possible systematic error if the assumption of gravitational dynamics is granted. Inclination relative to a flattened system may cause a systematic underestimate of the central mass by a factor $\sim (h/r)^2$, where $h/r$ is the aspect ratio of the flattening. The coupled effects of a broad radial emissivity distribution, an unknown angular radiation pattern of line emission, and sub-optimal sampling in the reverberation experiment can cause additional systematic errors as large as a factor of 3 or more in either direction.
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机译:在假设宽发射线气体的动力学受黑洞的重力支配的假设的基础上,估计了许多活跃银河核中中心黑洞的质量。最常用的方法是从混响映射实验中估算特征尺寸标尺$ r _ * $并将其与从线轮廓中获取的特征速度$ v _ * $结合起来;然后,推断的质量由$ r_ * v _ * ^ 2 / G $估算。我们批判性地讨论了支持重力动力学假设的证据,并发现这些论点仍然没有定论。然后,如果考虑了重力动力学的假设,我们将探讨可能的系统误差的范围。相对于扁平化系统的倾斜可能导致中心质量的系统低估$ \ sim(h / r)^ 2 $,其中$ h / r $是扁平化的纵横比。在混响实验中,宽的径向发射率分布,未知的线辐射角辐射图和次优采样的耦合效应可能导致在任一方向上附加系统误差高达3或更大。
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