Mapping the ionised gas in active galactic nuclei with spectral-timing and spectroscopy

The cores of most galaxies harbour a supermassive black hole. The process of its growth, manifested by the accretion of the surrounding material, is connected with the formation of a complex environment and the release of substantial amounts of energy. As a result, this region near the central black hole can reach luminosity far exceeding that of the host galaxy. These compact yet energetic cores of galaxies are called active galactic nuclei (AGNs). Spectroscopic observations of AGNs unveil several characteristic components shaping this region and often allow for placing general constraints on their spatial structure. Detailed mapping of this environment remains, however, a challenging task. Yet it is an essential one, as uncovering the underlying geometry and physical processes forming AGNs is key for understanding not only the black hole growth but also the impact AGNs have on their surroundings: observations reveal a tight connection between the supermassive black hole and the properties of its host galaxy. A crucial role in this connection is believed to be played by outflows of photoionised gas accelerated away from the central region. Despite being detected in most AGNs, the fundamental physical properties of these outflows are largely unconstrained, which poses a longstanding challenge to understanding these phenomena. In this thesis, I aim to overcome it by harnessing the power of photoionisation modelling of the ionised gas combined with the analysis of the time-dependent behaviour of the observed spectral features.