Efectos del calentamiento nocturno y calentamiento a largo plazo en poblaciones antárticas de deschampsia antarctica (magnoliophyta: poaceae).
Date
2024
Authors
Journal Title
Journal ISSN
Volume Title
Publisher
Universidad de Concepción
Abstract
Las galaxias enanas esferoidales son el tipo de galaxia enana con luminosidad más baja encontradas alrededor de la Vía Láctea. Corresponden a los sistemas más antiguos y con mayor dominación de materia oscura conocidos, ofreciendo una oportunidad única de explorar la formación de las primeras galaxias y el comportamiento de la materia oscura en pequeñas escalas. La formación de estos objetos es un debate en curso, mientras variedad de modelos intentan explicarlo, encuentran problemas con los escenarios de galaxias aisladas. Assmann et al. (2013) propuso un escenario para las enanas esferoidales, en donde cúmulos estelares se disuelven dentro de un halo de materia oscura. Luego, Aravena et al. (2019) adaptó este modelo para las enanas esferoidales débiles y ultra débiles, donde inicialmente las estrellas de la galaxia están distribuidas en un patrón fractal dentro del centro del halo de materia oscura, construyendo el componente luminoso débil observado. Probamos un escenario de formación por colapso (no se encuentra en equilibrio virial) modelando la galaxia enana esferoidal ultra débil Ursa Mayor II a través de simulaciones numéricas utilizando el Astrophysical Multipurpose Software Environment (AMUSE), con las estrellas siguiendo una distribución fractal dentro de un halo de materia oscura que corresponde a una distribución de Plummer. Obtenemos un objeto de forma no esférica, cuyo tamaño depende completamente del radio del fractal inicial y solamente se volverá estable cuanto este radio sea mayor a la longitud de escala del halo de materia oscura. Para reproducir el radio de la mitad de la masa de Ursa Mayor II, necesitaríamos un radio fractal entre 350-450 pc. Obtuvimos dispersiones de velocidades mayores a la observada, dependiendo de ambos, el radio fractal y de Plummer.
The dwarf spheroidal galaxies are the lowest luminosity dwarf galaxies found around the Milky Way. They are the oldest and most dark matter-dominated systems known, offering an unique chance to explore the formation of the first galaxies and the behavior of dark matter on small scales. The formation of these objects is an on-going debate, while several models try to explain it, they have problems with an isolated scenario. Assmann et al. (2013) proposed a scenario for dwarf spheroidals, where star clusters dissolve within a dark matter halo. Then, Aravena et al. (2019) adapted this model to faint and ultra-faint dwarf spheroidals, where initially the stars of the galaxy are distributed in a fractal pattern within the center of the dark matter halo, building the faint luminous component observed. We tested a collapsing (non viral equilibrium) formation scenario modelling the ultra-faint dwarf spheroidal galaxy Ursa Major II by performing numerical simulations using the Astrophysical Multipurpose Software Environment (AMUSE), with the stars following a fractal distribution within a dark matter halo corresponding to a Plummer distribution. We obtain an object of non spherical shape, which size depends completely on the initial fractal radius and will become stable only when this radius is larger than the dark matter halo scale-length. To reproduce UMa II’s half mass radius, we would need a fractal radius between 350-450 pc. We obtain velocity dispersions higher than observed, depending on both, fractal and Plummer radius.
The dwarf spheroidal galaxies are the lowest luminosity dwarf galaxies found around the Milky Way. They are the oldest and most dark matter-dominated systems known, offering an unique chance to explore the formation of the first galaxies and the behavior of dark matter on small scales. The formation of these objects is an on-going debate, while several models try to explain it, they have problems with an isolated scenario. Assmann et al. (2013) proposed a scenario for dwarf spheroidals, where star clusters dissolve within a dark matter halo. Then, Aravena et al. (2019) adapted this model to faint and ultra-faint dwarf spheroidals, where initially the stars of the galaxy are distributed in a fractal pattern within the center of the dark matter halo, building the faint luminous component observed. We tested a collapsing (non viral equilibrium) formation scenario modelling the ultra-faint dwarf spheroidal galaxy Ursa Major II by performing numerical simulations using the Astrophysical Multipurpose Software Environment (AMUSE), with the stars following a fractal distribution within a dark matter halo corresponding to a Plummer distribution. We obtain an object of non spherical shape, which size depends completely on the initial fractal radius and will become stable only when this radius is larger than the dark matter halo scale-length. To reproduce UMa II’s half mass radius, we would need a fractal radius between 350-450 pc. We obtain velocity dispersions higher than observed, depending on both, fractal and Plummer radius.
Description
Tesis presentada para optar al grado académico de Licenciado en Astronomía
Keywords
Galaxias enanas, Dinámica estelar, Colapso gravitacional