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arXiv 1807.07641astro-ph.GAastro-ph.HE
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局域宇宙中低光度类星体（LLQSO）中心引擎的X射线观测

An X-ray view of central engines of low luminosity quasars (LLQSO) in the local Universe

Sibasish Laha, Ritesh Ghosh, Matteo Guainazzi, Alex G. Markowitz

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Published in the MNRAS journal
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摘要：

我们对低光度类星体（LLQSO）样品进行了系统的X射线光谱分析，以研究这些源的中心引擎的性质。光学选择的LLQSO样本包括密切的，已知的明亮的活动星系核（AGN），作为一个重要的联系之间的强大的类星体在高红移和本地塞弗特星系。我们发现，尽管低红移类星体的辐射热光度比高红移类星体低近一个数量级，但它们的爱丁顿速率分布$λ_{\rm Edd}$是相似的。我们检测到$α_{\rm OX}$和$L_{2500 \rm Å}$之间的强反相关性，在其他几个大样本量的类星体研究中也检测到了这一点，这表明随着源的紫外光度增加，X射线光度降低。我们在LLQSO的X射线光谱中没有检测到任何显著的中性遮蔽（$N_{\rm H} \ge10^{22}\, \rm cm^{-2}$），因此排除了遮蔽是其较低光度的可能原因。我们的结论是，中心引擎的LLQSO功能类似的高红移类星体，和差异可能是因为事实上，LLQSO有较低的黑洞质量。我们没有发现宿主星系中的分子气体与活动星系核的吸积态之间有任何相关性。这表明LLQSO的宿主星系中分子气体的存在不会显著影响其SMBH的瞬时吸积速率。

英文摘要：

We have carried out a systematic X-ray spectral analysis of a sample of low luminosity quasars (LLQSO) to investigate the nature of the central engines of these sources. The optically-selected LLQSO sample consists of close, known bright active galactic nuclei (AGN) which serves as an important link between the powerful quasars at higher redshift and local Seyfert galaxies. We find that although the bolometric luminosities of the LLQSOs are lower than those of the higher redshift quasars by almost an order of magnitude, their distribution of the Eddington rate $λ_{\rm Edd}$ is similar. We detect a strong anti-correlation between $α_{\rm OX}$ and $L_{2500 \rm Å}$, as has also been detected in several other quasar studies with large sample sizes, indicating that as the UV luminosity of the source increases, the X-ray luminosity decreases. We do not detect any significant neutral obscuration ($N_{\rm H} \ge10^{22}\, \rm cm^{-2}$) in the X-ray spectra of the LLQSOs, and hence rule out obscuration as a possible cause for their lower luminosity. We conclude that the central engines of the LLQSOs function similarly to those of the higher redshift quasars, and the difference is possibly because of the fact that the LLQSOs have lower black hole masses. We do not find any correlation between the molecular gas in the host galaxies and accretion states of the AGN. This indicates that the presence of molecular gas in the host galaxies of the LLQSOs does not significantly influence the instantaneous accretion rates of their SMBHs.

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