用射电喷流和星系作宇宙弦探针

发布时间：2018-05-04 16:46

本文选题：引力透镜-射电喷流-星系-宇宙弦 + 大尺度结构　；参考：《南京大学》2011年硕士论文

【摘要】：弱引力透镜作为研究宇宙学的一种观测手段已经发展得相当成熟,并且已经被用于探测暗物质、暗能量以及宇宙大尺度结构的相关参数。这种效应因其只与透镜天体的引力场有关,因而比较适合用于探测宇宙弦等具有特殊引力效应的物质。许多理论都预言了宇宙弦的存在,并给出了理论的预期。在观测上,微波背景辐射,大尺度结构,引力波探测已经对宇宙弦的参数给出了一定限制。而且微引力乃至强引力透镜技术也被用于某些背景天体来探测宇宙弦,但至今仍无法证实宇宙弦的存在。而弱引力透镜技术将给宇宙弦的探测开辟一个新的窗口。本文研究了宇宙弦的弱引力透镜效应并给出了一些探测宇宙弦的方法。Konberg教授首次提出用射电喷流的引力扭曲作为探测透镜天体的技术,并且用“准线破缺因子”作为透镜效应的特征参量。我们把这种特征参量用于探测无限长扭曲弦的引力形变。然后,透过研究喷流的非常数偏转角,我们发现“准线破缺因子”与喷流的斜率有关。如果宇宙弦存在的话,在“平方公里阵列”(SKA)的样本中大概有3个喷流具有明显的观测信号(ηGG10°)。我们也研究了椭球天体的引力形变并且运用数值方法进一步研究了星系的轴向角分布和椭率分布。我们发现当背景星系的方向与宇宙弦的方向平行的时候,我们就得到了一个与椭率分布模型无关的形如“v”的轴向角分布。而且研究发现这些具有特殊位置的样本星系在宇宙弦作用下会变得更圆,使得它们的椭率分布发生显著变化。通过数值统计比较两种统计量的信噪比,我们发现椭率的分布变化较轴向的分布变化更为明显。椭率的分布变化可以在现有的巡天样本如斯隆数字巡天(SDSS)中得以检验,而轴向分布变化的检验有待于将来更大的巡天数据的公布,比如Large Synoptic Survey Telescope (LSST)和Dark Energy Survey (DES)。这些巨大的巡天样本可以对宇宙弦的分布和性质给出更强限制。
[Abstract]:Weak gravitational lensing as a cosmological observation method has been developed quite mature and has been used to detect dark matter dark energy and the relevant parameters of cosmic large-scale structure. Because this effect is only related to the gravitational field of a lens object, it is more suitable for detecting materials with special gravitational effects such as cosmic strings. Many theories predict the existence of cosmic strings and give theoretical expectations. In observation, microwave background radiation, large scale structure and gravitational wave detection have limited the parameters of cosmic string. Microgravity and even strong gravitational lensing are also used to detect cosmic strings in some background objects, but the existence of cosmic strings has not yet been confirmed. The weak gravitational lensing technology will open a new window for the detection of cosmic strings. In this paper, the weak gravitational lensing effect of cosmic strings is studied and some methods for detecting cosmic strings are given. Professor Konberg proposed for the first time that the gravitational distortion of radio jet current can be used as the technique of detecting lensed celestial bodies. In addition, the "criterion breaking factor" is used as the characteristic parameter of the lens effect. We use this characteristic parameter to detect the gravitational deformation of infinitely long twisted strings. Then, by studying the non-constant skew angle of the jet, we find that the "criterion breaking factor" is related to the slope of the jet. If the cosmic strings exist, about three of the samples of the "square kilometer array" SKA have obvious observational signals (畏 GG10 掳). We also study the gravitational deformation of ellipsoidal bodies and further study the axial angular distribution and ellipticity distribution of galaxies by numerical method. We find that when the direction of the background galaxy is parallel to the direction of the cosmic string, we obtain an axial angular distribution such as "v" which is independent of the ellipticity distribution model. Moreover, it is found that these sample galaxies with special positions become more circular under the action of cosmic strings, resulting in a significant change in their ellipticity distribution. By comparing the signal-to-noise ratio of the two statistics, we find that the variation of ellipticity distribution is more obvious than that of axial distribution. The variation of ellipticity distribution can be tested in the existing aerial survey samples such as Sloan Digital aerial Survey (SDSS), while the axial distribution change is to be verified by the publication of larger survey data in the future, such as Large Synoptic Survey Telescope / LSST) and Dark Energy Survey / DSS. These large aerial surveys can impose greater restrictions on the distribution and properties of cosmic strings.
【学位授予单位】：南京大学
【学位级别】：硕士
【学位授予年份】：2011
【分类号】：P111

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