Accretion properties of supermassive black holes across cosmic time and luminosities

This thesis comprehensively explores Active Galactic Nuclei (AGN) since cosmic noon and down to the lowest luminosities, utilizing a multiwavelength approach spanning X-ray to radio wavelengths. A key contribution is a method leveraging narrowband data from the miniJPAS survey, enabling the characterization of AGN properties while constraining their host galaxies. Robust physical parameters for X-ray-selected AGN up to z∼2.5 are derived. The analysis includes the examination of accretion ratios, a comparison with their proxies, and a forward modeling approach for assessing coevolution scenarios relative to local relations. Another significant contribution is a novel SED fitting module tailored for Low-Luminosity AGN (LLAGN), accurately characterizing their properties. Validated with diverse AGN samples, this module proves effective even in scenarios with galaxy contamination. The derived X-ray bolometric correction and exploration of UV-X-ray relations for LLAGN are presented. We further explore the host galaxy contamination problem and the possible impact of LLAGN on their host galaxies' specific star formation rate. The thesis concludes with a case study on how an LLAGN influences the interstellar medium of its host galaxy. High-resolution observations of the spiral galaxy M58 unveil H2 emission from warm molecular gas, indicating suppressed star formation in the inner kiloparsecs. Dust molecules remain unaffected compared to more luminous AGN. Optical forbidden line ratios suggest heating by low-velocity shocks caused by a low-power radio jet, highlighting the significant impact of LLAGN feedback on their host galaxies.