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arXiv 1107.2979astro-ph.HE
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低光度活动星系核的光学/紫外和X射线发射的关系

The relation of optical/UV and X-ray emission in low-luminosity active galactic nuclei

Ya-Di Xu

摘要:

本文利用28个Seyfert星系和21个低电离核发射线区(LINER)共49个源,研究了低光度活动星系核(LLAGNs)的光、紫外和X射线辐射的关系,这些源的光、紫外光谱光度λ= 2500 nm,\leq \log L_{v(2500 nm))(erg/s/Hz)\leq 27.7,以及在2 keV下的X射线光谱光度20.5 \leq \log L_{ν(2 keV)} \leq 25.3。发现活动星系核的X射线光度与光学/紫外X射线指数α ox之间存在很强的相关性,其斜率与以往工作中对活动星系核的研究结果非常相似。α_{ox}和L_{ν(2keV)之间的相关性很弱,与以往大多数类似工作中发现的发光活动星系核的相关性一样。我们还研究了$α_{ \rm ox}与爱丁顿比L_{bol} / L_{Edd}的关系,发现L_{bol} / L_{Edd} \lesssim = 10^{-3}的源具有显著的反相关,这与发光活动星系核的两个变量之间的相关相反。使用平流为主的吸积流(ADAF)模型,我们大致再现这两个变量的LLAGNs的反相关。这一结果有力地支持了ADAF作为LLAGNs吸积模式的候选者。

英文摘要:

We study the relation of optical/UV and X-ray emission in the low luminosity active galactic nuclei (LLAGNs), using a sample of 49 sources including 28 local Seyfert galaxies and 21 low-ionization nuclear emission-line regions (LINERs) with the optical/UV spectral luminosity at the wavelength λ=2500Å, 23.0\leq \log L_{ν(2500Å)(erg/s/Hz)\leq 27.7, and the X-ray spectral luminosity at 2 keV, 20.5\leq \log L_{ν(2 keV)}\leq 25.3. The strong correlations are found between the X-ray luminosity and the optical/UV to X-ray index, α_{ox}, with the optical/UV luminosity, with the slopes very similar to the findings for the luminous AGNs in the previous works. The correlation between α_{ox} and L_{ν(2 keV) is very weak as that found for the luminous AGNs in the majority of previous similar works. We also study the relation between $α_{\rm ox} and the Eddington ratio L_{bol}/L_{Edd} for our sample and find a significant anti-correlation for the sources with L_{bol}/L_{Edd}\lesssim 10^{-3}, which is opposite to the correlation between the two variables for the luminous AGNs. Using the advection dominated accretion flow (ADAF) model, we roughly reproduce this anti-correlationship for the two variables for the LLAGNs. This result strongly supports the ADAF as a candidate accretion mode in LLAGNs.

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