Browsing by Author "Gupta, Kriti Kamal"

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    BASS. LIII. The Eddington Ratio as the Primary Regulator of the Fraction of X-Ray Emission in Active Galactic Nuclei
    (2025) Gupta, Kriti Kamal; Ricci, Claudio; Tortosa, Alessia; Temple, Matthew J.; Koss, Michael J.; Trakhtenbrot, Benny; Bauer, Franz E.; Treister, Ezequiel; Mushotzky, Richard; Kammoun, Elias; Papadakis, Iossif; Oh, Kyuseok; Rojas, Alejandra; Chang, Chin-Shin; Diaz, Yaherlyn; Jana, Arghajit; Kakkad, Darshan; Moral Castro, Ignacio del; Peca, Alessandro; Powell, Meredith C.; Stern, Daniel; Urry, C. Megan; Harrison, Fiona
    Active galactic nuclei (AGN) emit radiation via accretion across the entire energy spectrum. While the standard disk and corona model can somewhat describe this emission, it fails to predict specific features such as the soft X-ray excess, the short-term optical/UV variability, and the observed UV/X-ray correlation in AGN. In this context, the fraction of AGN emission in different bands (i.e., bolometric corrections) can be useful to better understand the accretion physics of AGN. Past studies have shown that the X-ray bolometric corrections are strongly dependent on the physical properties of AGN, such as their luminosities and Eddington ratios. However, since these two parameters depend on each other, it has been unclear which is the main driver of the X-ray bolometric corrections. We present here results from a large study of hard-X-ray-selected (14–195 keV) nearby (z < 0.1) AGN. Based on our systematic analysis of the simultaneous optical-to-X-ray spectral energy distributions of 236 unobscured AGN, we found that the primary parameter controlling the X-ray bolometric corrections is the Eddington ratio. Our results show that, while the X-ray bolometric correction increases with the bolometric luminosity for sources with intermediate Eddington ratios (0.01–1), this dependence vanishes for sources with lower Eddington ratios (<0.01). This could be used as evidence for a change in the accretion physics of AGN at low Eddington ratios.
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    BASS. LIV. Physical Properties of AGN-hosting Galaxy Mergers from Multiwavelength SED Fitting
    (2025) Troncoso Balbiano, Marco Javier; Treister, Ezequiel; Rojas, Alejandra; Boquien, Médéric; Bauer, Franz; Koss, Michael J.; Assef, Roberto J.; Parra Tello, Miguel Agustín; Moral-Castro, Ignacio del; Ricci, Claudio; Dai, Sophia; Oh, Kyuseok; Ricci, Federica; Peca, Alessandro; Urry, C. Megan; Gupta, Kriti Kamal; Venturi, Giacomo; Signorini, Matilde; Mushotzky, Richard; Sanders, David
    Galaxy mergers are believed to play an important role in triggering rapid supermassive black hole (SMBH) growth. As merging nuclei approach each other, the physical properties of the participating galaxies and the associated SMBH growth are expected to evolve significantly. This study measures and characterizes these physical properties throughout the merger sequence. We constructed multiwavelength Spectral Energy Distributions (SEDs) from hard X-rays to the far-infrared (FIR) for a sample of 72 nearby Active Galactic Nuclei (AGN) host galaxies. The sample comprises 64 interacting systems, 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, aimed to derive critical physical properties. 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 (5.1), AGN luminosities (2.4), and nuclear obscuration (2.8) compared to earlier stages, supporting previous findings and reinforcing the link between merger-driven galaxy evolution and SMBH growth.