Radio Jets And Galaxies As Cosmic String Probes

As an observational technique for cosmological research, weak gravitational lens-ing has been developed for a long time. It has been used in Dark Matter detection, Dark Energy detection and Large Scale Structure research. Because it is only affected by gravitational field, it is appropriate for probing objects with special qualities, such as cosmic strings.Many theories predict the existence of cosmic string and the corresponding pa-rameters as well. Many observations, such as CMB, Large Scale Structure and grav-itational wave test, have already put constraints on the abundance of cosmic strings. Moreover, the observations from micro lensing and strong lensing have also been used to probe cosmic strings. However, there is no convinced evidence for the existence of cosmic strings. Thus, weak lensing observation of cosmic strings would open a new window for this research.In this paper, the lensing effect of a cosmic string is studied, and some new meth-ods are proposed to detect a cosmic string. The technique for using the jet as extended gravitational lensing probe was firstly explored by Kronberg. We use the "alignment-breaking parameter" as a sensitive indicator of gravitational distortion by a wiggly cos-mic string. Then, we applied the non-constant deflection angle to jets, and "alignment-breaking parameter" is just related to the projected slope of jets. About three jets in the sample of Square Kilometre Array (SKA) would have significant signals (ηG>10°) if a wiggly infinite cosmic string existed.The distortion of elliptical object is also studied and used to do a statistical re-search on directions of axes and ellipticities of galaxies. We find that the ellipticity axis distribution changes into a "v-type" one when we choose galaxies in some special position. This signal is independent of ellipticity distribution models. We also find some galaxies who are significantly lensed by wiggly strings appear to be rounder for an observer and the distribution of apparent ellipticity changes correspondingly. These variations of distributions serve as probes to detect wiggly strings and the future sur-vey, such as Large Synoptic Survey Telescope (LSST) and Dark Energy Survey (DES), would probably increase the power of these methods.