Physical properties of AGN-Hosting Galaxy Mergers from Multiwavelength SED Fitting
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2025
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Abstract
Galaxy mergers are believed to play an important role in triggering the rapid growth of supermassive black holes (SMBHs). As merging nuclei approach each other, the physical properties of the participating galaxies and the associated SMBH growth are expected to evolve significantly. In this thesis, we aim to measure and characterize these physical properties throughout the merger sequence, in this case for systems hosting actively growing SMBHs. We constructed multiwavelength Spectral Energy Distributions (SEDs) from hard X-rays to far-infrared (FIR) wavelengths, for a sample of 72 nearby Active Galactic Nuclei (AGN) host galaxies. The sample comprises 64 interacting systems with merging features, including single AGNs in mergers and dual AGNs, with nuclear separations <30 kpc, as well as eight isolated active galaxies with merging features. We carefully adapted available photometric measurements at each wavelength to account for their complex morphologies and varying spatial resolutions, to perform SED fitting using CIGALE (Code Investigating GALaxy Emission) software, aiming to derive the physical properties of these galaxies from their photometric SEDs. Our results reveal that merging galaxies hosting AGN(s) show deviations from the star-forming main sequence, and a wide range of star formation rates (SFRs). Both AGN activity and star formation are significantly influenced by the merger process, but these effects are more prominent in major, mass ratios <4:1, interactions. We find that the projected nuclear separation is not a good tracer of the merger stage. Instead, morphological classification accurately assesses the merger progression. Based on this morphological analysis, late-stage mergers exhibit elevated SFRs (5.1x), AGN luminosities (2.4x), and nuclear obscuration (2.8x) compared to earlier stages, supporting previous findings and reinforcing the link between merger-driven galaxy evolution and SMBH growth.
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Tesis (MSc in Astrophysics)--Pontificia Universidad Católica de Chile, 2025