Lick AGN监测项目2011:外宽线区域的Fe II混响
The Lick AGN Monitoring Project 2011: Fe II Reverberation from the Outer Broad-Line Region
摘要:
活动星系核光谱中突出的宽Fe II发射混合物已被证明会随连续变化而变化,但过去试图测量光学Fe II线的混响滞后时间的尝试只取得了有限的成功。在这里,我们报告的Fe II混响在两个塞弗特1星系,NGC 4593和Mrk 1511,从一个程序在利克天文台在2011年春天进行的数据的基础上检测。光曲线的发射线,包括H-β和Fe II的测量通过应用拟合例程分解成几个连续谱和发射线组件的光谱,我们使用互相关技术来确定混响滞后的发射线相对于V波段光曲线。在这两种情况下,Fe II的测量滞后(t_cen)比H-β长,尽管推断的滞后对拟合中使用的Fe II模板的选择有些敏感。对于使用Veron-Cetty等人(2004)的Fe II模板进行的光谱分解,我们发现NGC 4593中的t_cen(Fe II)/t_cen(H-β)= 1.9 ± 0.6,Mrk 1511中为1.5 ± 0.3。Fe II和连续发射之间的高度相关的变化的检测表明,在这些星系中的Fe II发射起源于光电离气体,主要位于外部分的宽线区域。
英文摘要:
The prominent broad Fe II emission blends in the spectra of active galactic nuclei have been shown to vary in response to continuum variations, but past attempts to measure the reverberation lag time of the optical Fe II lines have met with only limited success. Here we report the detection of Fe II reverberation in two Seyfert 1 galaxies, NGC 4593 and Mrk 1511, based on data from a program carried out at Lick Observatory in Spring 2011. Light curves for emission lines including H-beta and Fe II were measured by applying a fitting routine to decompose the spectra into several continuum and emission-line components, and we use cross-correlation techniques to determine the reverberation lags of the emission lines relative to V-band light curves. In both cases the measured lag (t_cen) of Fe II is longer than that of H-beta, although the inferred lags are somewhat sensitive to the choice of Fe II template used in the fit. For spectral decompositions done using the Fe II template of Veron-Cetty et al. (2004), we find t_cen(Fe II)/t_cen(H-beta) = 1.9+-0.6 in NGC 4593 and 1.5+-0.3 in Mrk 1511. The detection of highly correlated variations between Fe II and continuum emission demonstrates that the Fe II emission in these galaxies originates in photoionized gas, located predominantly in the outer portion of the broad-line region.
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