Instituto de Astrofísica

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Browsing Instituto de Astrofísica by Author "Barrientos, Luis Felipe"

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    A VLT/MUSE galaxy survey towards QSO Q1410 : looking for a WHIM traced by BLAs in inter-cluster filaments
    (2018) Pessa Gutiérrez, Ismael Alejandro; Tejos, Nicolás; Barrientos, Luis Felipe; Pontificia Universidad Católica de Chile. Instituto de Astrofísica
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    Enhanced 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 Astrofísica
    Upcoming 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.
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    Evolution of the Galaxy Cluster Red Sequence from Redshift 0.2 to 1.5
    (2022) Gutiérrez Hernández, Lorena; Barrientos, Luis Felipe; Pontificia Universidad Católica de Chile. Instituto de Astrofísica
    In this thesis, we present a study of the population of early-type galaxies in 115 clusters at 0.2 < z < 1.5, imaged with the F200LP/UVIS and F110W/IR filters of the Wide Field Camera 3 on the Hubble Space Telescope. We aim to investigate the evolution of the red sequence parameters (zero-point, slope, and intrinsic scatter) in the color-magnitude plane to constrain its members’ history and epoch of star formation. To accomplish this, we carefully selected the galaxies belonging to the red sequence, dismissing all contamination from the background and late-type galaxies into the clusters. Then, we used a robust linear fitting method to obtain the red sequence parameters in the rest frame. Finally, we compared the evolution of the zero-point with that of the color in stellar population synthesis models with different metallicity, formation red-shift, and e-folding time. We find that, as the redshift increases, the zero-point moves towards blue, the slope becomes steeper, and the observed scatter increases. On the other hand, the mean color of the clusters evolves slowly and is highly similar in systems at the same redshift, located in random directions in the universe. Therefore, the change of the zero-point is in agreement with the passive evolution of early galaxies in the present cosmological scenario. At the same time, we attribute the slope evolution to archaeological downsizing in conjunction with the progressive build-up of the red sequence. Finally, we constrain the epoch and period of stellar population formation to a strip diagonally crossing the τ - zf plane.
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    Studying the nature of ionizing sources during reionization
    (2025) Moya Sierralta, Cristóbal; Barrientos, Luis Felipe; Infante Lira, Leopoldo; Pontificia Universidad Católica de Chile. Instituto de Astrofísica
    La reionización es una época clave en la historia del universo. Sin embargo, aún no es claro cuales son los mecanismos responsables de esta. A la vez se desconoce la naturaleza del proceso en si. Esta tesis busca identificar las fuentes detras la reionización y caracterizar sus propiedades.Para lograr eso, estudiamos imágenes de banda angosta para seleccionar galaxias en la época de la reionización. Luego estudiammos en detalle una fuente confirmada mediante espectroscopía de mediana resolución. Finalmente, usando espectroscopía proporcionada por el telescopio espacial James Webb, logramos analizar la luz óptica de estos sistemas.Nuestras observaciones de banda angosta resulta en una función de luminosidad consistente con resultados anteriores los cuales sugieren que el universo está casi completaente ionizado a $z\sim 6.9$. Además, encontramos una sobredensidad de "\lya emitters" (LAEs) en el campo.Espectroscopía de mediana resolución de un LAE confirmado a $z\sim 6.9$ revela un perfil de linea complejo. Su alta luminosidad, ancho equivalente combinado con la morfología de la linea indican que esta fuente es un agente ionizante activo. Espectroscópia en el marco de referencia óptico de LAEs en un proto-cúmulo nos permite medir la metalicidad de estas. Nuestro resultados muestran que dichas galaxias poseen metalicidades menores comparado con galaxias locales y que la relación masa-metalicidad evoluciona con el corrimiento al rojo.Encontramos que los "\lya emitters" (LAEs) son una poblacion importante en la producción de radiación ionizante. A la vez encontramos que estás galaxias son capaces de generar volumenes ionizados a su alrededor. Finalmente, vemos como los LAEs son sistemas extremos, con baja metalicidad y altas temperaturas, condiciones favorables a la producción y escape de radiación ionizante.