Radio Jets and Galaxies as Cosmic String Probes

TL;DR

This paper explores new methods to detect cosmic strings through gravitational lensing effects on jets and galaxy ellipticities, proposing observational strategies for future surveys like SKA, LSST, and DES.

Contribution

It introduces the alignment-breaking parameter as a sensitive indicator and applies it to jets and galaxy ellipticities, enhancing detection prospects for cosmic strings.

Findings

Jets would show significant lensing signals if cosmic strings exist.

Galaxy ellipticity distributions are affected by cosmic strings, providing a statistical detection method.

Future surveys can effectively use these signals to detect or constrain cosmic string abundance.

Abstract

The lensing effect of a cosmic string is studied, and some new methods are proposed to detect the cosmic string. The technique for using jets as extended gravitational lensing probes was firstly explored by Kronberg. We use the "alignment-breaking parameter" $ \eta_G $ as a sensitive indicator of gravitational distortion by a wiggly cosmic string. Then, we applied the non-constant deflection angle to jets, and $ \eta_G $ of a specific jet is just related to the projected slope of the jet. At least three jets in the sample of Square Kilometer Array (SKA) would have significant signals ($ \eta_G >10^\circ $) if the wiggly infinite cosmic string existed. The distortion of elliptical object is also studied and used to do a statistical research on directions of axes and ellipticities of galaxies. In the direction of the string, we find that galaxies appear to be more elliptical for an observer and the distribution of apparent ellipticity changes correspondingly. Ellipticity distribution of current SDSS spiral sample has the signal-to-noise ratio up to 8.48 which is large enough for astronomical observations. The future survey, such as Large Synoptic Survey Telescope (LSST) and Dark Energy Survey (DES), would weaken the requirement of special geometry in the data processing. As a result, all kinds of distributions, including ellipticity axis distribution, would serve as probes to detect wiggly strings in the near future. In brief, if a wiggly cosmic string existed, these signals would be convenient to be observed with the future weak lensing survey or other surveys in deep space. If there was no lensing signal in these distributions, it would give the upper limit of the abundance of infinite strings.