Instituto de Astrofísica

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Browsing Instituto de Astrofísica by browse.metadata.categoria "Matemática física y química"

Now showing 1 - 4 of 4
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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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    Exploring 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 Astrofísica
    We 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.
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    Stochastic ion acceleration by the ion cyclotron instability in collisionless plasmas with a growing magnetic field
    (2018) Ley Quinteros, Francisco Javier; Reisenegger, Andreas; Riquelme Hernández, Mario Alejandro; Pontificia Universidad Católica de Chile. Facultad de Física
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    The 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 Astrofísica
    Extragalactic 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).