Browsing by Subject "Radio galaxies polarization"

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    The Ionized Intergalactic Medium and its Influence on Galaxies and Galaxy Clusters
    (2017-06) Lamee, Mehdi
    In this thesis, we studied physical and evolutionary aspects of the intergalactic medium throughout the universe. We used the archived Subaru telescope data and measured the ionization radiation escape fraction of 207 \lya\ emitting galaxies at $z\simeq 3.3$ in the SXDS field which does not contain any known overdensity region. Our stacking analysis enabled us to put strong limits on the IGM-absorption-corrected UV--to--LyC flux ratio $>13.8$ (3$\sigma$). The average ionizing radiation relative escape fraction is $f_{esc,rel}^{LyC} < 20\%$ (3$\sigma$), assuming an intrinsic $F_{\rm UV}/F_{\rm LyC}=3$. These limits indicate that the cluster and field populations of \lya\ emitters show different properties in their ionizing emissivity. In chapter \ref{spasschapter}, we study the influence of the intervening IGM on depolarizing the synchrotron radiation of radio galaxies. We combined observations of the NVSS at 1.4 GHz and the S-PASS at 2.3 GHz for 533 extragalactic radio sources with total intensity $I_{2.3}>420$ mJy. We found that fractional polarization, $\pi$, depends on the source magnetic field disorder, spectral index, size and depolarization. The relationship between the latter three shows that depolarization occurs primarily in the source vicinity. The intrinsic magnetic field disorder is the dominant mechanism responsible for the low $\pi$ of radio sources at high frequencies. Objects with $\pi_{1.4}\approx \pi_{2.3} \ge 4\%$ typically have simple Faraday structures and therefore, are most useful for studying foreground Faraday screens. At the end, we present deep and high-resolution L-band VLA observations of diffuse radio relics and filaments in the ICM of Abell-2255 merging galaxy cluster. We discovered three thin filaments close to the X-ray center of the cluster and at the tip of the tails of two radio galaxies. The spectral analysis of two filaments suggest that the responsible seed electrons belong to the tail of the same galaxy and have experienced an adiabatic compression due to a passing weak shock with Mach number $M\sim1.1$. We discovered two substructures and a new relic in the southern part and west of the NE relic. In addition, the alignment of three sources, C1, C2 and the Bridge suggests they might be remnants of a giant radio galaxy.