Estimates of AGN black hole mass and minimum variability timescale
Estimates of AGN black hole mass and minimum variability timescale
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DOI：
10.1088/1009-9271/5/5/004
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发表时间：
2005-10
期刊：
影响因子：
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通讯作者：
G. Xie;Luo Chen;Huai-zhen Li;L. Mao;H. Dai;Z. Xie;Li Ma;SB Zhou
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文献类型：
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作者：
G. Xie;Luo Chen;Huai-zhen Li;L. Mao;H. Dai;Z. Xie;Li Ma;SB Zhou
黑洞质量是活动星系核（agn）的基本物理参数之一，目前已经提出了许多估算方法。其中一种方法假定宽线区域（BLR）受到中心黑洞势的引力约束，因此可以通过轨道半径和多普勒速度估计黑洞质量。另一组方法假设观测到的变异性时间标度是由史瓦西黑洞或克尔黑洞周围最内层稳定轨道附近的轨道时间标度决定的，或者由吸积盘的特征时间标度决定的。我们收集了21个agn样本，获得了它们的最小变率时间尺度，并通过恒星速度色散或BLR大小-光度关系很好地估计了它们的黑洞质量（M,）。利用最小变率时间尺度，我们用三种不同的方法估计了21个天体的黑洞质量，结果分别用M-s、M-k和M-d表示。分别与M-sigma进行了比较，发现：(1)利用Kerr黑洞理论的最小变率时间尺度，M-sigma与M-k的差异很小，不超过一个数量级，平均差值约为0.53个指数；(2)使用史瓦西黑洞理论的最小变率时间尺度，导致M-sigma和M-s之间的差异较大，21个源中有6个源大于一个数量级，平均差值为0.74指数；(3)在吸积盘理论的最小变率时间尺度下，M-sigma和M-d之间的差异要大得多，21个源中有13个源的差异大于两个数量级；平均差值高达约2.01个指数。
Black hole mass is one of the fundamental physical parameters of active galactic nuclei (AGNs), for which many methods of estimation have been proposed. One set of methods assumes that the broad-line region (BLR) is gravitationally bound by the central black hole potential, so the black hole mass can be estimated from the orbital radius and the Doppler velocity. Another set of methods assumes the observed variability timescale is determined by the orbital timescale near the innermost stable orbit around the Schwarzschild black hole or the Kerr black hole, or by the characteristic timescale of the accretion disk. We collect a sample of 21 AGNs, for which the minimum variability timescales have been obtained and their black hole masses (M,) have been well estimated from the stellar velocity dispersion or the BLR size-luminosity relation. Using the minimum variability timescales we estimated the black hole masses for 21 objects by the three different methods, the results are denoted by M-s, M-k and M-d, respectively. We compared each of them with M-sigma individually and found that: (1) using the minimum variability timescale with the Kerr black hole theory leads to small differences between M-sigma and M-k, none exceeding one order of magnitude, and the mean difference between them is about 0.53 dex; (2) using the minimum variability timescale with the Schwarzschild black hole theory leads to somewhat larger difference between M-sigma and M-s, larger than one order of magnitude for 6 of the 21 sources, and the mean difference is 0.74 dex; (3) using the minimum variability timescale with the accretion disk theory leads to much larger differences between M-sigma and M-d, for 13 of the 21 sources the differences are larger than two orders of magnitude; and the mean difference is as high as about 2.01 dex.