活动星系核的光变非对称性探究

发布时间：2018-12-18 21:54

【摘要】：来自开普勒空间望远镜的高质量测光数据,使得以前所未有的时间分辨率分析活动星系核的光学光变成为可能。研究光变中的非对称性特征可以为限制活动星系核光变的物理模型提供独立的限制。在这篇论文中,我们使用了19个活动星系核的开普勒望远镜观测数据以分析其光变非对称性。光变曲线的有限观测长度会使低频光变具有选择效应,而此选择效应会同时对高频光变的非对称性判断产生干扰,我们通过高通滤波改正方法减弱这种影响。文中引入基于结构函数的非对称性参数β以对非对称性进行定量描述,β的不确定度则通过使用扩展的蒙特卡罗模拟方法予以估计。结果中,在1-20天的时间尺度上,样本中的观测源个体没有呈现出明显的非对称性特征。而将19个活动星系核的数据平均之后,在1～5天上的平均非对称性参数为0.00±0.03,在5～20天上则为-0.02±0.04,统计上均接近于0。类星体和塞弗特星系的子样本得到了相似的非对称性参数。我们的分析结果表明活动星系核的短期光学光变是高度对称的。我们还利用SDSS Stripe 82的多波段测光数据,对8944个类星体在颜色光变上的非对称性进行了检验。直接从观测数据中得到的结果显示,在数十天的时间尺度上类星体的‘变暗变红’趋势比‘变亮变蓝’趋势更加显著。但两种趋势的差异并不是物理的,而是测光数据中系统性颜色偏移的反映。如果将这一颜色偏移扣除,则类星体的‘变暗变红’与‘变亮变蓝’趋势之间几乎没有区别,即类星体的颜色光变行为是对称的。此外,借助于XMM-Newton卫星和GALEX卫星的观测,我们还计算了更短波长上活动星系核光变非对称性的显著水平。经过高通滤波改正并排除随机噪声干扰后,17个塞弗特星系的X射线数据在103～104秒上的平均非对称性参数为-0.01±0.02。而对于GALEX样本中的5434个类星体,在1～100天的时标上,其近紫外和远紫外波段的平均非对称性分别为-0.06±0.08和-0.01±0.06。这些结果显示活动星系核在X射线与紫外波段的光变也是对称的,更好的限定则有赖于观测设备测光精度的提高。
[Abstract]:High quality photometric data from the Kepler Space Telescope make it possible to analyze optical light from active galactic nuclei at unprecedented temporal resolution. The study of asymmetric characteristics in light variability can provide an independent limit for the physical model of limiting the light variability of active galaxy nuclei (AGNs). In this paper, we use Kepler telescope observations of 19 active galactic nuclei to analyze their light asymmetry. The limited observation length of the optical curve will make the low-frequency phototransformer have a selective effect, which will also interfere with the asymmetric judgment of the high-frequency phototransformer. We use the high-pass filter correction method to reduce this effect. In this paper, the asymmetric parameter 尾 based on structure function is introduced to describe the asymmetry quantitatively, and the uncertainty of 尾 is estimated by using extended Monte Carlo simulation method. The results show that the observed source individuals in the sample do not exhibit significant asymmetrical characteristics on the time scale of 1-20 days. After averaging the data of 19 active galactic nuclei, the average asymmetry parameters in 1 and 20 skies were 0.00 卤0.03 and -0.02 卤0.04, respectively, which were statistically close to 0. Subsamples of quasars and Seifert galaxies have obtained similar asymmetric parameters. Our results show that the short-term optical light transition of AGNs is highly symmetric. Using the multiband photometry data of SDSS Stripe 82, we also tested the asymmetry of 8944 quasars in color light variation. The results obtained directly from the observational data show that the trend of 'darkening to redness' of quasars is more significant than that of 'bright to blue' on a time scale of several decades. But the difference between the two trends is not physical, but a reflection of systematic color offset in photometry data. If this color shift is deducted, there is almost no difference between the trend of 'dark to red' and 'bright and blue' of the quasar, that is, the color light change behavior of the quasar is symmetrical. In addition, with the help of observations from XMM-Newton and GALEX satellites, we have also calculated the significant levels of asymmetry in the light of active galaxy nuclei at shorter wavelengths. After the correction of high-pass filtering and the elimination of random noise interference, the average asymmetry parameters of X-ray data of 17 Seifert galaxies in 103 ~ 104 seconds are -0.01 卤0.02. For 5434 quasars in the GALEX sample, the average asymmetry in the near ultraviolet and far ultraviolet bands was -0.06 卤0.08 and -0.01 卤0.06, respectively, on a time scale of 1 ~ 100 days. These results show that the light changes of the active galactic nuclei in the X ray and ultraviolet bands are also symmetrical, and the better limitation depends on the improvement of the photometric accuracy of the observation equipment.
【学位授予单位】：中国科学技术大学
【学位级别】：硕士
【学位授予年份】：2016
【分类号】：P157.6

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