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Cosmic voids of the Universe Large Scale Structure: finding, population, active galactic nuclei and magnetic fields

Work number - M 57 AWARDED

Elyiv Andrii, Cand. Sci. in Phys.&Math., Doctoral Student

of the Department of Extragalactic astronomy and astroinformatics,

the Main Astronomical Observatory of the National Academy of Sciences of Ukraine


The aim of the work is to study the cosmic voids as the largest objects in the Universe, their structure, processes inside and around them. In this series of works, many factors such as the Large-scale structure of the Universe, the distribution of galaxies, the phenomena of Active Galactic Nuclei (AGN) and blazars weretaken into account.

The author, on the basis of theoretical studies and numerical simulations, developed two new void finder approaches: based on geometric criteria and dynamical properties of the Large-scale structure of the Universe using the Lagrangian-Zeldovich approximation. A possibility to estimate magnetic field in cosmic voids was shown and a stability of relativistic electromagnetic cascade in them caused by gamma-photons from blazars was obtained.

The author investigated the correlation properties in distribution of AGN observed in the X-ray range, showing the dependence of their properties on the surrounding environment. Namely, on the basis of the XXL extragalactic survey(space telescope XMM-Newton), it has been demonstratedthat the AGN in rich galaxy clusters have a harder X-ray spectrum than ones in sparse regions on the edge of voids.

Author created algorithms and software for the identification of different structures of the Universe at various scales: cosmic void, isolated galaxies, groups of galaxies and agglomerates of galaxies. The proposed void finder shows 60% better significance of the allocated voids than the current ZOBOV analog. Numerical simulations of electromagnetic cascade in voids weredeveloped. Namely, the author considered an interaction of relativistic electron-positron pairs with a microwave and infrared background in cosmic voids. A tool for simulation of blazar images in gamma-rays for known Cherenkov telescopes was created. Author showed that modern Cherenkov telescopes are able to estimate the intergalactic magnetic field in voids in the range of inductions from 10-16 to 10-12 G.

This work is important for definition of a cosmological model of the Universe, in particular, the contstrains on its parameters, such as the content of dark matter, dark energy, the primordial magnitude of intergalactic magnetic field etc.

Number of publications:22 articles in foreign journals. According to the Scopus database, the total number of references to author's publications presented in the series work, is 323, h-index = 11; According to the Google Scholar database, the total number of references to author's publications presented in the series of work is 488, the h-index = 11. Author is going to defend doctoral thesis on topic presented in this work.