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- ItemUsing Multi-wavelength Correlations to Understand the Nearby structures in Strongly accreting AGN(2025) Flores Sanchez, Miryam Paola; Bauer, Franz Erik; Puzia, Thomas H.; Pontificia Universidad Católica de Chile. Instituto de AstrofísicaEste trabajo explora los posibles cambios en las distintas estructuras que componen los núcleos galácticos activos (AGNs) a través de un enfoque multibanda. Se compiló una muestra de 63000 cuásares (QSOs) seleccionados ópticamente del Sloan Digital Sky Survey (SDSS) DR10, con corrimientos al rojo z ≤ 1. Esta muestra fue cruzada con las líneas de emisión [OIII] λ5007A provenientes de los espectros del SDSS-DR9, fotometría en el infrarrojo medio (MIR) del catálogo AllWISE y fotometría en rayos X del catálogo 3XMM-DR4, lo que dio lugar a múltiples sub- conjuntos de contrapartes. Analizamos las relaciones entre las luminosidades L(2keV ), L(12μm), L(2500A) y L(5007A), las cuales trazan diferentes componentes del AGN: el disco de acreción (UV), la corona (rayos X), el toro polvoriento (MIR) y la región de líneas angostas o cono de ionización ([OIII]). Estas correlaciones permiten investigar cómo varía la estructura del AGN en función de su luminosidad intrínseca, reflejando potencialmente cambios en parámetros como la masa del agujero negro, la tasa de acreción, la altura del toro y la geometría de ionización. Trabajos previos como Steffen et al. (2006) y Asmus et al. (2015) se utilizan como referencias clave para contextualizar y comparar nuestros resultados.Los múltiples subconjuntos se clasificaron en fuentes con “good photometry” (i.e., detected sources) y fuentes con “insufficient photometry” (i.e., upper limits). Estos límites superiores ayudan a acotar el espacio de parámetros y a revelar posibles sesgos observacionales. Construimos diagramas de luminosidad en los formatos L vs. L y L/L vs. L, aplicamos ajustes de Regresión Ortogonal por Distancias (ODR) a las fuentes detectadas. También se construyeron histogramas de estas distribuciones para calcular los anchos a mitad de altura (FWHM), y se utilizaron coeficientes de correlación de Pearson para cuantificar la fuerza de cada relación. Si bien las relaciones L vs. L muestran correlaciones sólidas y consistentes, las relaciones L/L vs. L permiten estudiar la eficiencia con la que distintos componentes del AGN reprocesan la radiación, revelando posibles variaciones estructurales con la luminosidad. Sin embargo, estas regresiones basadas en las tasas no siempre se alinean con las tendencias observadas en los gráficos L vs. L. La fuerte dependencia de la distancia presente en el eje X (logL) podría ampliar de forma engañosa la pendiente de las regresiones basadas en las tasas de luminosidad, lo que sugiere que las tendencias observadas en los diagramas L/L vs. L podrían deberse en gran parte a un efecto inducido por la distancia más que a una correlación intrínseca real. Nuestros resultados muestran una tendencia decreciente en L(12μm)/L(2500A) con el aumento de la luminosidad UV, en concordancia con las predicciones del modelo del toro en retroceso. Además, a medida que la luminosidad UV aumenta, el cono de ionización parece ampliarse y la luminosidad [OIII] aumenta en consecuencia. Sin embargo, dado que L([OIII]5007A) permanece sistemáticamente por debajo tanto de L(2500A) como de L(12μm), los datos sugieren que los conos de ionización no están completamente llenos de gas y polvo. En cambio, la emisión probablemente se origina en material concentrado a lo largo de las superficies de los conos, y no en todo su volumen. Estos hallazgos se ven respaldados por la tendencia adicional observada en L(12μm)/L([OIII]5007A) vs. L(2500A), y se confirman visualmente en la Figura 3.12, donde se ilustra el comportamiento geométrico combinado del toro y del cono de ionización. Se requiere una mejor resolución espacial y espectral en los rangos infrarrojo y óptico para poder resolver completamente estas estructuras internas de los AGNs y validar los escenarios propuestos.
- ItemThe ALeRCE LC Classifier transient sample from 5 yrs of ZTF alerts(2025) Correa Orellana, Javier Ignacio; Bauer, Franz Erik; Catelan, Márcio; Pontificia Universidad Católica de Chile. Facultad de Física. Instituto de AstrofísicaExtragalactic transients such as supernovae are some of the most powerful phenomena in the universe, and have enabled multiple studies in thefields such as star formation and stellar evolution beyond the Milky Way,nucleosynthesis and cosmology. Specifics on their progenitors are still anopen question, and host galaxies can provide important context, since theirstellar populations are linked to potential progenitors.Theadvent of unbiased wide-field surveys has provided homogeneous samples of transients, with machine learning codes helping to leverage as muchinformation as possible. In this pursuit, we assembled a sample of transients from the Automatic Learning for the Rapid Classification of EventsLight Curve Classifier discovered by the Zwicky Transient Facility between2018 and 2023, including 22627 transients out to z∼0.5, with 7269 having spectroscopic classifications in the Transient Name Server. Transientswere associated to their host galaxies, for which we extracted photometry,collected redshifts, and fit them with spectral energy distributions to derive physical properties such as stellar mass and star formation rate. Thesefeatures, along some regarding their light curves shapes and peaks, werecompiled into a catalog for publication, one of the largest of its kind.The catalog was used to assess transient properties and transient-hostrelations from the literature. We found consistency with previous worksregarding transient luminosities and physical properties of their host galaxies, with higher statistical significance given the larger sample size. Theseresults set important precedents for the future (e.g., Rubin Observatory).
- ItemPhysical properties of AGN-Hosting Galaxy Mergers from Multiwavelength SED Fitting(2025) Troncoso Balbiano, Marco Javier; Treister, Ezequiel; Pontificia Universidad Católica de Chile. Instituto de AstrofísicaGalaxy 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.
- ItemHigh-Resolution Optical IFU Spectroscopy of the Complex Galaxy Merger II Zw 096(2025) Riesco Bravo, Clemente; Treister, Ezequiel; Pontificia Universidad Católica de Chile. Instituto de AstrofísicaLuminous and Ultra-luminous IR galaxies ((U)LIRGs) are critical for investigating feedback mechanisms due to a combination of intense star formation (SF) episodes and active galactic nuclei (AGN) in the context of complex galaxy interactions. We conduct a detailed analysis of the local(z = 0.0365) merging system II Zw 096 using the Multi-Unit Spectroscopic Explorer (MUSE) on the Very Large Telescope (VLT), combining high-resolution Narrow Field Mode (NFM) and wide-area Wide Field Mode (WFM) observations. We mapped the morphology, kinematics, and ionizing radiation of the system’s gas by fitting atomic emission lines, and analysed the kinematics, age, and metallicity of the stellar population by fitting the continuum. We identify three or more distinct galaxies within II Zw 096, in contrast to previous studies suggesting the presence of only two. Our analysis reveals rotational patterns in the gas and stellar components, as well as complex interactions consistent with a collapsing small galaxy group. The kinematics and ionization structures suggest high star formation rates, shock-driven processes and post-Starburst events, which align with this proposed scenario. Focusing on the D1 compact region, which contributes 40–70% of the system’s IR emission, and combining information from archival multi-wavelength observations from Chandra and ALMA, we find strong evidence for the presence of a heavily obscured AGN powering it. Our analysis of the internal structure, interactions, and merger state of II Zw 096 offers novel insights into the galaxy evolution processes taking place in this dynamic and highly chaotic system.
- ItemEnhanced pixelated modeling of group and cluster scale lenses: Getting ready for Vera Rubin(2025) Urcelay Solís de Ovando, Felipe José; Barrientos, Luis Felipe; Jullo, Eric; Pontificia Universidad Católica de Chile. Instituto de AstrofísicaUpcoming wide-field surveys like LSST and Euclid will uncover thousands of strong gravitational lenses, enabling statistical studies of lens properties, tracing mass distributions from galaxies to clusters, and probing cosmology. While automated modeling exists for galaxy-scale lenses, group- and cluster-scale systems remain challenging due to their complexity.We present a fast, automated method for modeling group and cluster strong lenses, optimized for LSST-like data. The approach combines a large-scale halo with subhalos defined by scaling relations and uses a third-order Taylor expansion for subhalo deflections to improve computational efficiency. The method is memory-light and scales independently of cluster richness.We validate the pipeline on 200 LSST-like simulated lenses (100 clusters, 100 groups), recovering unbiased halo parameters and accurate total masses. Performance improves when selecting lenses with bright arcs or radial features. Application to real SGAS systems yields results consistent with previous models.We discuss possible applications of this method, such as constraining the halo mass function, inner slope of clusters, and subhalo properties. We also outline the necessary extensions for modeling Euclid lenses, which require increased source complexity due to the higher resolution.