Browsing by Subject "intracluster medium"
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Item The Dynamics of Radio Galaxies In Clusters: Morphological Interactions and Particle Evolution(2020-06) Garon, AveryIn this thesis, I explore the dynamics of radio galaxies in galaxy clusters by studying the statistical influence of the intracluster medium on the morphology of radio galaxies, and the evolution of the electron populations within different galaxies and radio relics in Abell 2255. In Chapter 2, I study the impact of cluster environment on the morphology of a sample of 4304 extended radio galaxies from Radio Galaxy Zoo. A total of 87% of the sample lies within a projected 15 Mpc of an optically identified cluster. Brightest cluster galaxies (BCGs) are more likely than other cluster members to be radio sources, and are also moderately bent. The surface density as a function of separation from cluster center of non-BCG radio galaxies follows a power law with index -1.10+-0.03 out to 10 r_500 (~7 Mpc), which is steeper than the corresponding distribution for optically selected galaxies. Non-BCG radio galaxies are statistically more bent the closer they are to the cluster center. Within the inner 1.5 r_500 (~1 Mpc) of a cluster, non-BCG radio galaxies are statistically more bent in high-mass clusters than in low-mass clusters. Together, I find that non-BCG sources are statistically more bent in environments that exert greater ram pressure. I use the orientation of bent radio galaxies as an indicator of galaxy orbits and find that they are preferentially in radial orbits. Away from clusters, there is a large population of bent radio galaxies, limiting their use as cluster locators; however, they are still located within statistically overdense regions. I investigate the asymmetry in the tail length of sources that have their tails aligned along the radius vector from the cluster center, and find that the length of the inward-pointing tail is weakly suppressed for sources close to the center of the cluster. In Chapter 3, I present a deep and high resolution P-band (370 MHz) VLA observation of the central radio galaxies and relics in Abell 2255. Using L-band (1.5 GHz) data analyzed in Lame'e (2017), I generate maps of spectral index, alpha_PL, calculated between the two frequencies. I detect two new extended sources of very steep spectrum (alpha_PL < -2) radio emission near the center of the cluster. I analyze the spectral curvature of the Original Tailed Radio Galaxy (TRG), the Goldfish galaxy, and the NE radio relic. The spectrum of the TRG and Goldfish both exhibit curvature intermediate between a power law spectrum and the exponential cut-off spectrum of the Jaffe-Perola model (Jaffe & Perola, 1973). There are two thin filaments at the end of the TRG; filament F1 only has a reliable measurement of the spectrum at one position, and is consistent with having the same spectral shape as the tail itself; the spectrum of filament F2 has less curvature than the tail, and is consistent with a power law. This suggests that F2 has been reaccelerated by a shock in the ICM, which would also explain its morphology, although that does not work for F1. The southern component of the NE relic has values of alpha_PL ranging between -0.4 and -1.4, consistent with previous observations across similar frequencies. Systematic problems with the in-band spectral index at 1.5 GHz make quantitative claims about the spectral curvature difficult, but the extremely steep values of alpha_LL are not consistent with a shock reaccelerated power law spectrum.Item The Ionized Intergalactic Medium and its Influence on Galaxies and Galaxy Clusters(2017-06) Lamee, MehdiIn 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.