Intensity Changes Of The Active Galactic Nucleus Optical Fe Ii Emission Lines Studied

In recent years, Active Galactic Nuclei or AGN is becoming a hot issue in astrophysical domain. FeII emission lines of AGN play a particularly important role in the AGN study. FeII emission lines can provide a useful probe of the the structure and internal physical condition of AGNs. Although the traditional photoionzation models can successfully explained the radiative mechanism of the most of broad emission lines of AGN, the photoionization models are frustrated in explaining the observed strength of FeII complex. The more reasonable models are needed to solve this difficulty. In addition, the strong variability of FeII emission lines is detected in some Seyfert galaxies, however, the variability behavior and the physical drivers of the FeII complex in Seyfert galaxies has been poorly understood. This dissertation including my three works focus on the FeII emission lines of AGN. The main conclusions of these researches are following.1. We re-analyzed the optical spectra of luminous Seyfert 1 galaxy Fairall 9 extracted from the AGN Watch program. We detected that there is no large scale variation of the FeII intensity compared with the increased continuum strength in the period of nine months. However, in the same time, the identified H β variations that clearly following the variations of continuum are detected. We firstly found the variability of R_Fe and a convincing intrinsic Baldwin Effect of the optical FeII blends in Fairall 9.2. The 6 high quality spectra of another Seyfert galaxy, Mark 376, are obtained by using NAOC 2.16m optical telescope in Xinglong observatory during 5 years. We analyzed these spectra and detected the properties of the FeII emission lines of Mark 376. A negative correlation between the variability of R_Fe and continuum flux is found in Mark 376. In the two works mentioned above, we found the negative correlation between the variability of R_Fe and continuum flux in both objects. These objects have relatively broad profiles of H β ( FWHM > 4000 km s^-1).3. In order to study the unified variation properties of R_Fe we observed a samplethat has about 130 Seyfert galaxies. Through the data analyzing, we obtained a dichotomy between the variability of Rpe and width of H 3 in these Seyfert galaxies. That is, some Narrow-Line Seyfert 1 galaxies (NLSls) have a positive correlation between R.Fe and continuum flux. In contrast, the other sources with negative correlation have relatively broad profiles of H P . This result supports the argument of Wang 2005.