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arXiv 2310.05089astro-ph.GAastro-ph.CO
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活动星系核中的宽线区:含尘埃还是无尘埃?

Broad-line region in active galactic nuclei: Dusty or dustless?

Ashwani Pandey, Bozena Czerny, Swayamtrupta Panda, Raj Prince, Vikram Kumar Jaiswal, Mary Loli Martinez-Aldama, Michal Zajacek, Marzena Sniegowska

AI总结:

该研究针对活动星系核宽线区是否含尘埃的问题,利用CLOUDY代码构建含尘与无尘模型,结合NGC 5548观测数据对比,发现低电离线形成于含尘区、高电离线形成于无尘区,且额外吸收体会改变Hβ发射区位置。

摘要:

研究背景:活动星系核中的尘埃明确以尘埃分子环面的形式存在于宽线区(BLR)的正外侧。不过,部分BLR模型预测尘埃也可能存在于BLR内部。研究目的:我们研究BLR对辐射的再处理过程,旨在观测尘埃的存在如何影响再处理后的连续谱以及发射线的性质。研究方法:我们使用CLOUDY光致电离代码,针对含尘埃和无尘埃的等离子体计算了一系列模型。我们重点关注了已被充分研究的天体NGC 5548,并将发射线等值宽度的预测结果与该天体的观测数据进行了对比。研究结果:当介质含尘埃时,对于由(Hβ的)时延测量和(Mg II的)半径-光度关系所推断的发射线距离,我们得到Hβ和Mg II线的预期等值宽度与NGC 5548的观测值大致吻合。我们发现入射辐射与观测者看到的辐射一致,因此内盘和BLR之间不需要存在屏蔽层。不过,像He II这类高电离线显然形成于内部的无尘埃区域。当存在额外吸收体时,Hβ发射区会向吸积盘表面的无尘埃部分靠近。

英文摘要:

Context. Dust in active galactic nuclei is clearly present right outside the broad-line region (BLR) in the form of a dusty molecular torus. However, some models of the BLR predict that dust may also exist within the BLR. Aims. We study the reprocessing of radiation by the BLR with the aim of observing how the presence of dust affects the reprocessed continuum and the line properties. Methods. We calculated a range of models using the CLOUDY photoionisation code for dusty and dustless plasma. We paid particular attention to the well-studied object NGC 5548, and we compared the line equivalent width predictions with the data from observations for this object. Results. We obtained a rough agreement between the expected equivalent widths of the H$β$ and Mg II lines and the observed values for NGC 5548 for the line distances implied by the time-delay measurement (for H$β)$ and the radius-luminosity relation (for Mg II) when the medium is dusty. We found the incident radiation to be consistent with the radiation seen by the observer, so no shielding between the inner disc and the BLR is required. High ionisation lines such as He II, however, clearly form in the inner dustless region. When the additional absorber is present, the H$β$ emitting region moves closer to the dustless part of the accretion disc surface.

机构、总结、中文摘要均由AI分析而来,可能存在错误,请以论文正文为准。

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