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arXiv 0808.4154astro-ph
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Seyfert Galerkin多波长研究中AGN贡献的约束

Constraining the AGN Contribution in a Multiwavelength Study of Seyfert Galaxies

M. Meléndez, S. B. Kraemer, H. R. Schmitt, D. M. Crenshaw, R. P. Deo, R. F. Mushotzky, F. C. Bruhweiler

摘要:

我们研究了103个Seyfert星系样品的高、低电离[O IV] λ 25.89 μ m、[Ne III] λ 15.56 μ m和[Ne II] λ 12.81 μ m发射线之间的关系,目的是限制活动星系核(AGN)和恒星形成的贡献。我们用[O IV]和[Ne II]辐射作为活动星系核功率和恒星形成的示踪物,研究了辐射线气体的电离状态。我们发现,Seyfert 2星系的[O IV]/[Ne II]比值平均比Seyfert 1星系的低。这一结果表明了两种可能的情况:1)Seyfert 2星系具有内在较弱的活动星系核,或2)Seyfert 2星系具有相对较高的恒星形成率比Seyfert 1星系。我们估计的分数[Ne II]直接与活动星系核,并发现,塞弗特2星系有一个更大的贡献,从恒星形成的一个因素,平均约1.5倍,比发现在塞弗特1星系。使用[Ne II]的恒星成分作为当前恒星形成的示踪剂,我们在Seyfert 1和Seyfert 2星系中发现了类似的恒星形成率。我们研究了中红外和远红外连续光谱,发现[Ne II]与60微米处的连续光谱光度有很好的相关性,而[Ne III]和[O IV]与25微米处的连续光谱光度的相关性比与更长波长处的连续光谱光度的相关性好,这表明中红外连续光谱光度主要由活动星系核控制,而远红外光度主要由恒星形成控制。总的来说,这些结果测试AGN的统一模型,并建议,塞弗特星系之间的差异不能仅仅是由于视角的依赖性。

英文摘要:

We have studied the relationship between the high- and low-ionization [O IV] lambda 25.89 micron, [Ne III] lambda 15.56 micron and [Ne II] lambda 12.81 micron emission lines with the aim of constraining the active galactic nuclei (AGN) and star formation contributions for a sample of 103 Seyfert galaxies. We used the [O IV] and [Ne II] emission as tracers for the AGN power and star formation to investigate the ionization state of the emission-line gas. We find that Seyfert 2 galaxies have, on average, lower [O IV]/[Ne II] ratios than those of Seyfert 1 galaxies. This result suggests two possible scenarios: 1) Seyfert 2 galaxies have intrinsically weaker AGN, or 2) Seyfert 2 galaxies have relatively higher star formation rates than Seyfert 1 galaxies. We estimate the fraction of [Ne II] directly associated with the AGN and find that Seyfert 2 galaxies have a larger contribution from star formation, by a factor of ~1.5 on average, than what is found in Seyfert 1 galaxies. Using the stellar component of [Ne II] as a tracer of the current star formation we found similar star formation rates in Seyfert 1 and Seyfert 2 galaxies. We examined the mid- and far-infrared continua and find that [Ne II] is well correlated with the continuum luminosity at 60 micron and that both [Ne III] and [O IV] are better correlated with the 25 micron luminosities than with the continuum at longer wavelengths, suggesting that the mid-infrared continuum luminosity is dominated by the AGN, while the far-infrared luminosity is dominated by star formation. Overall, these results test the unified model of AGN, and suggest that the differences between Seyfert galaxies cannot be solely due to viewing angle dependence.

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