Low-Luminosity Active Galactic Nuclei at the Highest Resolution: Jets or Accretion Flows?
Low-Luminosity Active Galactic Nuclei at the Highest Resolution: Jets or Accretion Flows?
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DOI：
10.1086/381313
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发表时间：
2003-11
期刊：
影响因子：
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通讯作者：
James M. Anderson;J. Ulvestad;L. Ho
中科院分区：
文献类型：
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作者：
James M. Anderson;J. Ulvestad;L. Ho
利用甚长基线阵列对6个低光度活动星系核进行了1.7 - 43 GHz（其中3个星系为2.3-15 GHz）多频成像。尽管在几个频带中的动态范围约为100，但所有六个星系仍然没有得到解决，其大小限制在8.4 GHz的103-104倍于银河系中心的史瓦西黑洞半径。星系光谱在1.7至43 GHz之间大致平坦，而不是在高频时陡峭到经典的光学薄同步加速器光谱。虽然光谱斜率有点类似于对流主导的吸积流的预测，但对于星系的黑洞质量来说，光度太高了，并且在高频下的轻微光谱陡峭不能用这种吸积流的标准简单模型来解释。相比之下，紧凑的喷流可以容纳平均光谱指数，相对较高的射电光度和未解决的外观，但只有在所有六个星系的喷流都相当接近我们的视线。这个约束是在协议的尘埃环统一模型的基础上的六个活动星系核的倾角预测。
Six low-luminosity active galactic nuclei (AGNs) have been imaged at multiple frequencies from 1.7 to 43 GHz (2.3-15 GHz for three of the galaxies) using the Very Long Baseline Array. In spite of dynamic ranges of about 100 in several frequency bands, all six galaxies remain unresolved, with size limits at 8.4 GHz of 103-104 times the Schwarzschild radii of the black holes inferred at their galactic centers. The galaxy spectra are roughly flat from 1.7 to 43 GHz, rather than steepening to classical optically thin synchrotron spectra at high frequencies. Although the spectral slopes somewhat resemble predictions for advection-dominated accretion flows, the luminosities are too high for the black hole masses of the galaxies, and the slight spectral steepening at high frequencies cannot be explained by standard simple models of such accretion flows. In contrast, compact jets can accommodate the average spectral index, the relatively high radio luminosity, and the unresolved appearance, but only if the jets in all six galaxies are fairly close to our line of sight. This constraint is in agreement with inclination angle predictions for five of the six AGNs based on the dusty torus unification model.