The radio sky harbours both galactic and extragalactic sources of arcminute- to degree-scale emission of various physical origins. To discover extragalactic diffuse emission in the Cosmic Web... Show moreThe radio sky harbours both galactic and extragalactic sources of arcminute- to degree-scale emission of various physical origins. To discover extragalactic diffuse emission in the Cosmic Web beyond galaxy clusters, one must image low–surface brightness structures amidst a sea of brighter compact fore- and background sources. Angularly separating the faint from the bright radio sky requires high-quality ionospheric calibration. This thesis introduces new advances in and investigations into ionospheric calibration, the degree-scale Milky Way foreground, and two sources of megaparsec-scale emission in cosmic filaments: giant galactic outflows and cosmological structure formation shocks. Giant galactic outflows (or ‘giant radio galaxies’) are generated by the jets of active supermassive black holes, and transport relativistic leptons, entrained atomic nuclei, heat, and magnetic fields from the centres of galaxies to their outskirts and beyond. These outflows embody the most energetic pathway by which galaxies respond to the Cosmic Web around them. Structure formation shocks around filaments are a generic, but still elusive, prediction of cosmological simulations and trace the gravitational flow of matter from proto-voids to filaments. Both phenomena inform on the strength, topology, and origin of magnetic fields in the Cosmic Web. Show less
At any given time, cosmic rays constantly shower the Earth from all direction. The origin of cosmic rays is still a mystery as their paths are deflected by magnetic fields to random directions. The... Show moreAt any given time, cosmic rays constantly shower the Earth from all direction. The origin of cosmic rays is still a mystery as their paths are deflected by magnetic fields to random directions. The most likely sources of cosmic rays are Gamma-Ray Bursts (GRB). As the most energetic events known in the universe, GRBs are the death throes of massive stars that end in the explosion of stellar materials into interstellar matters. The interactions between cosmic rays and materials surrounding the GRB can produce neutrinos and very-high energy gamma-rays. Studying these high-energy neutrinos and gamma-rays can enlighten us further on the origin of cosmic rays. Very-high energy gamma rays can be observed by very large volume neutrino telescopes such as ANTARES in the Mediterranean Sea and IceCube in the South Pole. This dissertation focuses on ANTARES telescope operated as a gamma-ray telescope, which is possible by searching for downgoing muons produced from the interaction of gamma-rays with the Earth's atmosphere. Analytical calculations necessary to estimate the rate of photon-induced muons from GRBs has been performed. The responses of the detector to downgoing muons have been understood by using Monte Carlo simulations. The findings also provide a discussion on the future prospect of this venture. Show less
