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- ItemMass Matters 2: Mass and metallicity dependence of the lithium content of Red Clump giants(2024) Del Moral Lobos, Almendra Paz; Chaname Domínguez, Julio César; Pontificia Universidad Católica de Chile. Facultad de FísicaIn this thesis, we study Lithium depletion, intending to better understand how mixing is involved in this process and how mass and metallicity affect its evolution.
- ItemPulsating stellar clocks: Mira variables on the far side of the Galactic disk(2024) Albarracín Contreras, Ricardo Rogelio; Zoccali, Manuela; Pontificia Universidad Católica de Chile. Instituto de AstrofísicaLa estructura y la cinemática del disco de la Vía Láctea se infieren en gran medida a partir de la vecindad solar. Para obtener una comprensión completa, es esencial encontrar trazadores confiables en regiones menos exploradas como el bulbo y el lado lejano del disco. Las variables Mira, que son velas estándar brillantes y bien estudiadas, ofrecen una excelente oportunidad para rastrear poblaciones intermedias y antiguas en estas regiones. Nuestro objetivo es aislar una muestra pura de variables Mira en el estudio Vista Variables en la Vía Láctea utilizando algoritmos de procesos gaussianos. Esta muestra se utilizará para estudiar poblaciones de edad intermedia y antigua en el bulbo galáctico y el disco lejano. Se procesó la fotometría de series temporales en el infrarrojo cercano y medio utilizando algoritmos de procesos gaussianos para identificar variables Mira y modelar sus curvas de luz. Calibramos criterios de selección con una muestra inspeccionada visualmente para crear una muestra de alta pureza de variables Mira, integrando fotometría multibanda y datos cinemáticos de movimientos propios. Presentamos un catálogo de 3.602 variables Mira. Al analizar la fotometría, las clasificamos según su química superficial rica en oxígeno o carbono y derivamos relaciones de extinción selectiva a total de A_{K_{s}}/E(J - K_{s}) = 0.471 \pm 0.01 y A_{K_{s}}/E(H - K_{s}) = 1.320 \pm 0.020. Usando la relación período-edad de las variables Mira, encontramos evidencia que respalda la formación de adentro hacia afuera del disco de la Vía Láctea. La distribución de movimientos propios y distancias se alinea con la curva de rotación galáctica y la cinemática del disco. Extendemos la curva de rotación hasta un radio galactocéntrico de aproximadamente 17 kpc y no encontramos evidencia fuerte del disco estelar nuclear en nuestra muestra de variables Mira. Este estudio constituye el catálogo más grande de estrellas variables en el lado lejano del disco galáctico hasta la fecha.
- ItemExploring Super-Chandrasekhar Supernova SN2007if with radiative transfer code TARDIS(2024) Silva Beyer, Joaquín; Clocchiatti, Alejandro; Pontificia Universidad Católica de Chile. Instituto de AstrofísicaSuper-Chandrasekhar Supernovae (SNe) are a peculiar case of Type Ia SNthat show very high luminosities, slow light-curve evolution, and low expan-sion velocities, consistent with progenitor masses over the Chandrasekharlimit (≳ 1.4M⊙). SN 2007if is one of those events, with a still unknownexplosion scenario. Its early spectra are smooth and near featureless, butat later epochs, they seem to morph into a normal Type Ia. I exploredits spectra with radiative transfer code TARDIS, using three models, con-sidering the envelope interaction and the violent merger hypotheses. Thebest model, based on the envelope interaction scenario, resulted in a verygood match for early epochs, and a better match in the later epochs than theother models. I performed abundance tomography and adapted its chemicalstructure, resulting in my model 07if-tail. While it had a good agree-ment with the observed low velocities and some lines, many still featuredtoo deep absorption profiles, and the lines suggested a lower temperaturethan the overall continuum. I found that SN2007if probably lacks S and hasno Fe on its outer regions. In order to explain SN2007if’s light curve andspectra, a secondary source of continuum brightness is needed. My findingssupport the scenario of a WD-WD slow merger, forming a CO envelope thatinteracts with the explosion’s ejecta.
- ItemAn experiment in near field cosmology: A search for the Magellanic Wake(2024) Cavieres Carrera, Manuel Antonio; Chanamé, Julio; Pontificia Universidad Católica de Chile. Instituto de AstrofísicaThe infall of the Magellanic Cloud system into the Milky Way halo hasstrong effects on the distribution of the stars and dark matter in the outerhalo of our Galaxy. In particular, N-body simulations predict a large-scaledensity asymmetry that spans the northern Galactic hemisphere (known as thecollective response), along with a localized overdensity (the Wake) that trailsthe LMC’s orbit. In this study, we collected wide-field deep near-infrared andoptical photometry from the VISTA and DECam instruments in four fieldsalong the expected position of the Magellanic Wake, covering most of thedensity range predicted to be found in the outer halo, as predicted by numericalmodels. This data allows us to select a clean sample of halo stars that reachthe oldest main sequence turn-off (MSTO) up to 100 kpc, with ∼ 400 stellarsources further than 60 kpc, on two separate tracers, near main sequence turnoff stars and red giant branch. We found that the Magellanic Wake overdensityis present in our data with a relative overdensity of 3.07 ± 0.7. Comparisonof the radial density profiles of near-MSTO stars with simulations of the MilkyWay/LMC interaction is best fitted by a massive LMC model with a total massof 2.5 × 10^11M⊙. This work provides the first unambiguous detection of thewake with consistent densities between two tracers.
- ItemExploring the Green Valley with the dark energy survey: studying the evolution of galaxies(2023) Gil Toriello, Santiago; Galaz, Gaspar; Pontificia Universidad Católica de Chile. Instituto de AstrofísicaWe investigate the properties of galaxies located at the so-called Green Valley, an intermediate region between the blue-cloud of active star- forming galaxies, and the red-sequence of quenched and "dead" galaxies, visible in a color vs stellar mass diagram for galaxies.We utilize data from multiple releases of the Dark Energy Survey (DES), to characterize galaxies based on their physical properties, and to correlate their location in a stellar mass vs color diagram with their morphologies.We selected a sample of high-quality photometric data from the Year 3 re- lease of the Dark Energy Survey, with redshifts ranging from local z ∼ 0, to intermediate z ∼ 1.5, and cleaned it by applying a set of different quality selection criteria. We obtained a number of measurements for the photometric redshifts of the galaxies, by employing different parametric algorithms, to study each evolution separately as a function of distance. With the use of LePHARE, a template fitting code, we measured a set of physical properties of the galaxies that are helpful to study their evo- lution, and to assess the transitional nature of galaxies inside the Green Valley. These are, mainly, the Absolute Magnitude, the Stellar Mass, the Star Formation Rate and the UV Luminosity.We made use of two catalogues for morphological prediction available for the Year 3 release. These catalogues allowed us to better constrain the relation between the morphological structures of galaxies and their evolutionary stage.Results show that combining SED template fitting algorithms with mor- phological analysis allows to constrain the bi-modality distribution even when working with optical surveys, up to redshifts of z = 1.5.This is a first approach on the use of these methods to pave the way more massive and intensive data treatment surveys, like the future LSST survey to be done with the Vera Rubin Telescope.