The Hot Atmospheres of X-shaped Radio Galaxies

We present an observational and numerical study of X-shaped radio galaxies, a subset of the double-lobed radio galaxies with a second set of lobes or "wings". These sources have been proposed as the "smoking gun" of supermassive black hole mergers, in which case the secondary lobes would be fossil remnants following a black hole spin-flip jet reorientation. However, they may instead originate in the interplay between giant radio lobes and their hot plasma environments, since radio lobes can be considered as bubbles of light fluid in the heavier intracluster medium. Circumstantial evidence from studies of the host galaxies at optical wavelengths indicates that this may indeed be the case, leading to two important questions we attempt to answer in this work: (1) Does it appear that X-shaped radio galaxies are aware of their environments? (2) Can radio galaxies respond to their environments in such a way as to form X-shaped morphology? We use radio, optical, and X-ray imaging data to investigate the first question, finding that, in general, X-shaped sources have jets co-aligned with the major axes of their hot (X-ray emitting) atmospheres and wings co-aligned with their minor axes. However, in at least one case (where the jet clearly does not follow this trend), a deep X-ray observation suggests that rapid reorientation of the jet axis is the best explanation. Moreover,despite the trend we discover, the hydrodynamic models of wing formation have significant theoretical problems. Thus, the second major component of this thesis is concerned with using hydrodynamical simulations to determine whether X-shaped radio galaxies can be produced in response to asymmetries in the atmosphere. We inject jets as light fluids into a model cluster or galactic atmosphere previously in hydrostatic equilibrium, thereby forming bubbles similar to those observed in radio galaxies. Since we inject the jet along the major axis of an asymmetric atmosphere, distortions to the canonical double-lobed radio galaxy result from different responses to the local pressure gradient. With a significantly anisotropic atmosphere and a powerful but decaying jet, we find that X-shaped morphology indeed results for reasonable jet and cluster parameters. However, it is unclear whether our simulated mechanism would be effectual in nature because of the high degree of anisotropy required and the differences between some observed wings and our model wings. We make a number of predictions which we would expect to be observed in the future if the hydrodynamic model is at work

Philosophical Self-Presentation in Late Antique Cappadocia

This dissertation offers a new perspective to the development of religious orthodoxy in the second half of the fourth century CE by examining the role of the body in the inter- and intra-religious battles between Christians and “pagans” over the claim to the cultural capital of philosophy. Focusing on Cappadocia (modern-day central Turkey), a particularly vital region of the fourth-century Roman empire, I argue that during this time, Greek-speaking intellectuals created and disputed boundaries between Christianity and “paganism,” as well as between “orthodoxy” and “heresy,” based on longstanding elite notions of how an ideal philosopher should look, think, and act. I offer a close reading of the works of three Christian bishops—Basil of Caesarea (d. 378), his friend Gregory of Nazianzus (d. 389/90), and his brother Gregory of Nyssa (d. 394/95)—alongside those of their “pagan” contemporary, the emperor Julian (d. 363). For both Julian and the Cappadocians, I argue, religious orthodoxy—whether Christian or “pagan”—was not simply a matter of doctrine. Rather, these elite authors claimed that correct religion manifested itself in bodily features such as physical appearance and behavioral habits. In the rhetoric of these men, to be a proper follower of the gods entailed not only holding correct opinions and performing correct rituals, but exercising one’s entire being in a way that made piety appear second-nature. Drawing on their common background in classical culture (paideia), the Cappadocians and Julian presented themselves as ideal philosophers, whose grasp of the “correct” knowledge and habits qualified them to serve as religious leaders. The notions of Christian theology and classical philosophy that they constructed were rooted as much in questions of habits, demeanor, and dress, as they were in questions of theology and knowledge

The Matter of Jerusalem: The Holy Land in Angevin Court Culture and Identity, \u3ci\u3ec\u3c/i\u3e. 1154-1216

This dissertation reshapes our understanding of the mechanics of nation-building and the construction of national identities in the Middle Ages, placing medieval England in a wider European and Mediterranean context. I argue that a coherent English national identity, transcending the social and linguistic differences of the post-Norman Conquest period, took shape at the end of the twelfth century. A vital component of this process was the development of an ideology that intimately connected the geography, peoples, and mythical histories of England and the Holy Land. Proponents of this ideology envisioned England as an allegorical new Jerusalem inhabited by a chosen people, and believed that England’s twelfth-century kings were also destined to rule the terrestrial kingdom of Jerusalem in the Holy Land. Drawing upon biblical history, local legends, crusading ideology, and eschatological beliefs, twelfth-century English writers strove to associate England with the Holy Land not only through the crusade movement, but also in the greater scope of Christian and mythic history. The prime movers behind these developments were attached to the courts of the so-called Angevin kings of England—Henry II (r. 1154-89) and his sons Richard I (r. 1189-99) and John (r. 1199-1216)—who were also counts of Anjou in France (hence, Angevin). While historians have long recognized these rulers’ contributions to the development of government institutions such as the exchequer and common law, I call attention to a crucial ideological movement that underlay these bureaucratic innovations in England. Ultimately, I argue that the Angevins’ active participation in the wider political and intellectual movements of twelfth-century Europe, the Mediterranean, and the Near East was essential to the creation of a unified English identity