Browsing by Author "Rojas, Alejandra"

Now showing 1 - 4 of 4
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    BASS XLIV. Morphological preferences of local hard X-ray selected AGNs
    (EDP Sciences, 2025) Parra Tello, Miguel Agustín; Bauer, Franz E.; Cicco, Demetra de; Doll, Goran; Koss, Michael; Treister, Ezequiel; Finlez, Carolina; Troncoso Balbiano, Marco Javier; Auge, Connor; Moral Castro, Ignacio del; Chung, Aeree; Gupta, Kriti K.; Kim, Jeein; Oh, Kyuseok; Ricci, Claudio; Ricci, Federica; Rojas, Alejandra; Caglar, Turgay; Harrison, Fiona; Powell, Meredith C.; Stern, Daniel; Trakhtenbrot, Benny; Urry, C. Megan
    We present detailed morphological classifications for the hosts of 1189 hard X-ray selected (14–195 keV) active galactic nuclei (AGNs) from the Swift-BAT 105-month catalog as part of the BAT AGN Spectroscopic Survey (BASS). BASS provides a powerful all-sky census of nearby AGNs, minimizing obscuration biases and providing a robust dataset for studying AGN-host galaxy connections. Classifications are based on a volunteer-based visual inspection workflow on the Zooniverse platform, adapted from the Galaxy Zoo DECaLS (GZD) project. Dual-contrast grz color composite images, generated from public surveys (e.g., NOAO Legacy Survey, Pan-STARRS, SDSS) and dedicated observations enabled key morphological features to be identified. Our analysis reveals that, with respect to a control sample of inactive galaxies, BASS AGN hosts show a deficiency of smooth elliptical galaxies (∼70%) and spiral galaxies with prominent arms (∼80%), while displaying an excess of mergers or disturbed systems (∼400%), and disk galaxies without a spiral structure (∼300%). These trends are found after controlling for redshift and i-band magnitude, which suggests a preference for AGN activity in gas-rich, dynamically disturbed environments or transitional disk systems. We also find a higher bar fraction among AGN hosts than in a control sample (∼50% vs. ∼30%). We further explore the relationships between AGN properties (e.g., X-ray luminosity, black hole mass, and Eddington ratio) and host morphology, and find that high-luminosity and high-accretion AGNs preferentially reside in smooth or point-like hosts. At the same time, lower-luminosity AGNs are more common in disk galaxies. These results underscore the importance of morphological studies in understanding the fueling and feedback mechanisms that drive AGN activity and their role in galaxy evolution. Our dataset provides a valuable benchmark for future multiwavelength surveys (e.g. LSST, Roman, and Euclid) and automated morphological classification efforts.
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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.
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    Molecular Gas in Major Mergers Hosting Dual and Single AGNs at
    (2025) Johnstone, Makoto A.; Treister, Ezequiel; Bauer, Franz E.; Chin-Shin Chang; Cicone, Claudia; Koss, Michael J.; Del Moral Castro, Ignacio; Muller Sanchez, Francisco; Privon, George C.; Ricci, Claudio; Scoville, Nick; Venturi, Giacomo; Barcos Muñoz, Loreto; Armus, Lee; Blecha, Laura; Casey, Caitlin; Comerford, Julia; Evans, Aaron; Kawamuro, Taiki; Medling, Anne M.; Messias, Hugo; Nagar, Neil; Rojas, Alejandra; Sanders, David; Trakhtenbrot, Benny; U, Vivian; Urry, Meg
    We present high-resolution (∼50–100 pc) Atacama Large Millimeter/submillimeter Array observations of 12CO(2–1) or 12CO(1–0) emission in seven local (z ≲ 0.05) major mergers—five of which are dual active galactic nucleus (AGN) systems, and two of which are single AGN systems. We model the molecular gas kinematics through rotating disk profiles using a Bayesian Markov Chain Monte Carlo approach. The residuals were then used to isolate nonrotating components of the molecular gas—the most likely contributor to future supermassive black hole (SMBH) growth. We find that more-massive SMBHs have higher surface densities of nonrotating molecular gas within their sphere of influence. This potential molecular gas supply, however, does not correlate with the current accretion efficiency of the SMBHs, suggesting that only a fraction of the observed nonrotating gas is currently reaching the SMBH. Finally, we tentatively find no significant differences in the nuclear molecular gas masses of single-AGN and dual-AGN hosts, both within the SMBH sphere of influence and within the central kiloparsec. Our results indicate that the probability of occurrence of the dual AGN phenomenon is likely dependent on AGN variability and/or obscuration rather than the availability of molecular gas in the nuclear regions.