High-redshift active galactic nuclei and their environment

Sammanfattning: In order to understand the formation and evolution of local massive galaxies and to reveal the processes that engineered the tight correlations found between their supermassive black hole (SMBH) mass and bulge mass or velocity dispersion, the study of powerful, high-redshift active galactic nuclei (AGNs) and their environment is crucial. AGNs are luminous targets providing important clues to galaxy evolution, as their central SMBH is growing at high rates, which opens the opportunity to unfold how the growth of the black hole influences the growth of its host galaxy. Moreover, powerful high-z AGNs are hosted by massive galaxies and likely trace protoclusters, where the progenitors of present-day massive galaxies reside. Observations of high-z quasars and radio galaxies suggest that these AGNs live in overdense environment surrounded by star-forming Lyman-alpha emitters and submillimetre galaxies. At smaller scales several high-z quasars and radio galaxies have gas-rich and/or star-forming companion galaxies. The aim of this thesis is to study the environment of high-z quasars and radio galaxies through submillimetre and CO spectral line observations and to contribute to the effort of uncovering the underlying processes that shape the evolution of massive galaxies. The thesis focuses on three case studies of high-z AGN-companion galaxy systems at z=2-3. These were selected based on the AGN host galaxy appearing as gas-poor, while the companion galaxy being very gas-rich. However, sensitive observations with the Atacama Large Millimeter/submillimeter Array and the Karl G. Jansky Very Large Array, tracing CO line emission and dust continuum emission, revealed that a significant amount of molecular gas and dust emission is associated with the host galaxies of the AGNs. My results highlight the importance of sensitive and high-resolution observations and demonstrate that high-z AGN systems are more complex and diverse, than it is implied by theoretical studies.