In this thesis new methodologies are developed for the detection and systematic study of radio sources in the early universe. This allows us to gain a deeper understanding of the formation and... Show moreIn this thesis new methodologies are developed for the detection and systematic study of radio sources in the early universe. This allows us to gain a deeper understanding of the formation and evolution of galaxies, the activity of supermassive black holes, and the final phase transition of our universe: the epoch of reionization. Using the Low Frequency Array (LOFAR) telescope, this thesis systematically investigates the low radio frequency properties of quasars, the brightest non-variable objects in our cosmos, in the first billion years after the Big Bang. Through the discovery of new radio quasars in the early universe and subsequent studies, this thesis shows the diversity within the quasar population and highlights the importance of multi-wavelength observations for our comprehension of the formation and evolution of active supermassive black holes and their impact on the surrounding environment. Show less
One of the key quests in astronomy is to study the growth and evolution of galaxies across cosmic time. Radio observations provide a powerful means of studying the formation of stars and subsequent... Show moreOne of the key quests in astronomy is to study the growth and evolution of galaxies across cosmic time. Radio observations provide a powerful means of studying the formation of stars and subsequent buildup of distant galaxies, in a way that is unbiased by the presence of dust. This thesis provides a detailed view of faint, star-forming galaxies in the early Universe through sensitive radio observations, and compiles several studies probing distant star formation with both radio synchrotron and free-free emission. In Chapter 2, we detect a large number of galaxies using sensitive new radio data from the Very Large Array, allowing us to separate radio emission from star formation and active galactic nuclei in the faint radio sky. In Chapter 3, we calibrate synchrotron emission as a tracer of star formation in distant starburst galaxies, while in Chapters 4 & 5 we turn towards radio free-free emission — a faint but very powerful tracer of star formation. Using sensitive new radio data at high frequencies, we perform the first detailed studies of free-free emission in distant galaxies. Show less
Wevers, T.; Pasham, D.R.; Velzen, S. van; Miller-Jones, J.C.A.; Uttley, P.; Gendreau, K.C.; ... ; Chiti, A. 2021
