Cosmic depth & detail: advancing LOFAR imaging workflows to unveil the deep high-resolution universe

This thesis utilises the exceptional sensitivity and resolution of LOFAR to explore the low-frequency Universe, while simultaneously advancing the telescope's capabilities to enable new scientific discovery. We first demonstrate LOFAR's capability to produce deep sensitive wide-field images of large-scale structures, presenting the deepest image to date of a known radio bridge between two merging galaxy clusters -- an effort aimed at uncovering its origin. Shifting to smaller scales, we exploit the high resolution of the Dutch LOFAR stations to investigate the cosmic evolution of extended radio-loud AGN morphologies. While this provides valuable insights, it also reveals limitations due to the resolution limits when using only the Dutch LOFAR stations. This inspires to the latter half of the thesis which focuses on the development of advanced data processing techniques to generate deep sub-arcsecond wide-field images using the entire European LOFAR array. This leads to the creation of the deepest sub-arcsecond wide-field image at 140 MHz, alongside cost-efficient methods to reduce the need for manual intervention and enable fully automated ultra-deep wide-field imaging at LOFAR's highest resolutions.<br>