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The cosmic evolution of galaxies and supermassive black holes (SMBHs) is believed to be correlated through interlinked physical processes. However, two aspects of the galaxy-BH correlation remain unclear: the fueling of actively accreting black holes (called Active Galactic Nuclei or AGNs) and the physical process of AGN feedback. Previous attempts to answer these questions using single-aperture spectra of galaxies have fallen short, as they can only consider the dominant excitation source in the spectrum and cannot rule out the involvement of other excitation sources such as supermassive black holes, star formation, and shock excitations. In this thesis, we present a novel solution to separate the mixing mechanisms in galaxy spectra analysis: a new theoretical three-dimensional (3D) diagram that can simultaneously separate star formation, AGN, and shocks in galaxies with integral field spectroscopy (IFU) data. This new 3D diagram incorporates the most up-to-date and self-consistent theoretical models for HII regions, AGN narrow-line regions, and the time-dependent shocks and precursor models. The inclusion of theoretical models in the new 3D diagram independently constrains the parameter space for each mechanism and provides information on the gas metallicity, ionization states, and shock velocity along with the separation. By applying this new 3D diagram, we obtain detailed maps of the mechanism distribution, gas metallicity, and ionization states for individual galaxies in nearby active galaxies in the S7, SAMI, and MaNGA surveys. With these results, we study how the contribution and spatial distribution of each power source change with the environment, stellar mass, and merger stages for the galaxies in mergers. This research shines a new light on the study of galaxy evolution, especially its coevolution with the growth of the central black hole. |
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