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arXiv 1107.0195astro-ph.COastro-ph.GAastro-ph.HE
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2型Seyfert星系核Fe Ka线核的Chandra高能光栅观测:与1型核的比较

Chandra High Energy Grating Observations of the Fe Ka Line Core in Type 2 Seyfert Galaxies: A Comparison with Type 1 Nuclei

Xinwen Shu, Tahir Yaqoob, Junxian Wang

摘要:

我们提出了一个研究的核心Fe Ka发射线在~6.4 keV的样品中的II型塞弗特星系的钱德拉高能光栅(HEG)观察。样本由10个独特来源的29个观测值组成。我们目前的Fe Ka线参数的测量与目前可用的最高光谱分辨率。特别是,我们得出了最强大的固有线宽的一些来源的样品中的日期。我们获得了10个源中的8个源的加权平均FWHM为2000 \pm 160 km/s(其余源的信噪比不足)。通过与分光偏振观测得到的光学发射线宽的比较,我们发现Fe Ka线发射材料的位置是光学BLR尺寸的~0.7-11倍。此外,与13个获得最佳Fe Ka线半高宽约束的I型活动星系核相比,我们发现它们的半高宽分布和平均半高宽没有差别,这一结论与中心黑洞质量无关.这一结果表明,大部分Fe Ka线发射可能起源于一个与引力半径相同的普遍区域,平均约为30,000 Rg。通过研究Fe K线光度与[O IV]线光度之间的相关性,我们发现I型和II型活动星系核的Fe K线流量有一定的差别,但L(Fe)与L([O IV])的比值相差约两个数量级。我们的研究结果证实了理论预期的Fe Ka发射线光度不能平凡地被用作代理的固有AGN光度,除非一个详细的比较数据与适当的模型被应用。

英文摘要:

We present a study of the core of the Fe Ka emission line at ~6.4 keV in a sample of type II Seyfert galaxies observed by the Chandra High Energy Grating (HEG). The sample consists of 29 observations of 10 unique sources. We present measurements of the Fe Ka line parameters with the highest spectral resolution currently available. In particular, we derive the most robust intrinsic line widths for some of the sources in the sample to date. We obtained a weighted mean FWHM of 2000 \pm 160 km/s for 8 out of 10 sources (the remaining sources had insufficient signal-to-noise). From a comparison with the optical emission-line widths obtained from spectropolarimetric observations, we found that the location of Fe Ka line-emitting material is a factor of ~0.7-11 times the size of the optical BLR. Furthermore, compared to 13 type I AGNs for which the best Fe Ka line FWHM constraints were obtained, we found no difference in the FWHM distribution or the mean FWHM, and this conclusion is independent of the central black hole mass. This result suggests that the bulk of the Fe Ka line emission may originate from a universal region at the same radius with respect to the gravitational radius, ~30,000 Rg on average. By examining the correlation between the Fe Ka luminosity and the [O IV] line luminosity, we found a marginal difference in the Fe K line flux between type I and type II AGNs, but the spread in the ratio of L(Fe) to L([O IV]) is about two orders of magnitude. Our results confirm the theoretical expectation that the Fe Ka emission-line luminosity cannot trivially be used as a proxy of the intrinsic AGN luminosity, unless a detailed comparison of the data with proper models is applied.

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