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2.4 Colisión De Galaxias Simulación de colisión de dos galaxias para estudiar la formación de las galaxias enanas esferoidales satélites de la Vía Láctea Omar Alfonso Bohórquez Pacheco Universidad Nacional de Colombia Facultad de Ciencias, Departamento de Física Bogotá, Colombia 2016 Simulación de colisión de dos galaxias para estudiar la formación de las galaxias enanas esferoidales satélites de la Vía Láctea Omar Alfonso Bohórquez Pacheco Trabajo de grado presentado como requisito parcial para optar al título de: Magister en Ciencias - Física Director: Dr. rer. nat. Rigoberto Casas Miranda Grupo de Investigación: Astrofísica Universidad Nacional de Colombia Facultad de Ciencias, Departamento de Física Bogotá, Colombia 2016 A mis padres y en especial a mi abuela Esther Vega viuda de Pacheco, sin su ayuda no hubiera sido posible. Posible es que me equivoque y tome por oro y diamantes lo que solo es cobre y vidrio. René Descartes Agradecimientos Un gran agradecimiento al CECAD - Centro de Computación de Alto Desempeño de la Universidad Distrital “Francisco José de Caldas” y a mis amigos José Benavides, Diana Judith Cubillos Jara y Yeimy Camargo, sin su ayuda no habría sido posible. Resumen y Abstract IX Resumen En la actualidad dentro del área de la astrofísica se presentan un sinnúmero de problemas sin resolver, entre ellos el problema del origen de las galaxias satélite de la VL. Estas galaxias se caracterizan por ser de tipo enana esferoidal. La mayoría de estas se encuentran distribuidas en una estructura tipo disco que se encuentra dispuesta de casi forma perpendicular al plano de la galaxia, esta estructura es conocida con el nombre de disco de satélites (DoS) o Vast Polar Structure Of Satellite Galaxies (VPOS). Hasta el momento no se ha podido encontrar un modelo que dé cuenta de la cantidad y de la distribución espacial de estas galaxias. Sin embargo se han presentado varias propuestas de solución para el caso de la VL, una de las cuales propone que estas tuvieron origen en la colisión de dos galaxias de disco hace miles de millones de años. En este trabajo se llevaron a cabo simulaciones numéricas de N-cuerpos con el software Gadget2 para colisiones entre dos galaxias de disco que pudieron dar origen al disco de satélites de la VL. Se puede decir que bajo las condiciones iniciales planteadas para estas simulaciones no es posible generar las características dinámicas y espaciales de lo que se denomina el disco de galaxias satélite la VL (DoS), sin embargo, esto no descarta por completo el modelo propuesto para este estudio, ya que si bien no refleja los resultados esperados, se pueden proponer trabajos futuros para realizar simulaciones y modificar los parámetros de impacto y las relaciones de masa y así poder enmarcar las condiciones físicas bajo las cuales sería posible este evento. Los resultados de este trabajo permiten acotar aún más el espacio de condiciones iniciales orbitales y de masa de eventuales progenitores del DoS de la VL. Palabras clave: Grupo Local, Galaxias Enanas, Vía Láctea X Colisión de dos Galaxias de Disco Abstract At present within the area of astrophysics there are a number of unresolved problems, including the problem of the origin of the satellite galaxies of the Milky Way. These galaxies are characterized by dwarf spheroidal galaxies type. Most of them are distributed in a disk-like structure which is arranged almost perpendicular to the plane of the galaxy, this structure is known as satellite disk (DoS) or Polar Structure Of Vast Satellite Galaxies (VPOS). So far there is not a model that fully reproduces the amount and spatial distribution of these galaxies. However there have been several proposed for the solutions, one of which suggests that these originated in the collision of two disk galaxies billions of years ago. In this work we have performed N-bodies numerical simulations of with Gadget2 of the collision between two disk galaxies that could give rise to disc of VL satellites. It can be said that under the initial conditions set for these simulations is not possible to generate dynamic and spatial characteristics of what is called the satellite the disc of Milky Way (DoS) galaxies, however, this does not preclude in any way the model proposed for this study because although it does not reflect the expected results can be proposed for future work simulations and modify the parameters of impact and the mass ratios to frame the physical conditions under which this event possible. The results of this work allow limiting further orbital space initial conditions and eventual mass progenitors of DoS VL. Keywords: Local Group, Dwarf Galaxies, Milky Way Contenido XI Contenido Pág. Resumen ........................................................................................................... IX Lista de figuras .............................................................................................. XIV Lista de tablas ............................................................................................ XXIV Introducción ....................................................................................................... 1 1. Galaxias, Grupo Local y Galaxias Satélites ................................................. 5 1.1 Galaxias ........................................................................................................... 5 1.1.1 Secuencia de Hubble .............................................................................. 6 1.1.2 Galaxias elípticas ................................................................................... 6 1.1.3 Galaxias espirales .................................................................................. 8 1.1.4 Galaxias irregulares ............................................................................... 9 1.1.5 Galaxias enanas ..................................................................................... 9 1.1.6 Vía Láctea (VL) ...................................................................................11 1.2 Grupo Local .................................................. ¡Error! Marcador no definido. 1.2.1 Distribución espacial del Grupo Local ..................................................16 1.2.2 Propiedades del Grupo Local ................................................................19 1.2.3 Galaxias enanas del Grupo Local ..........................................................22 1.3 Galaxias enanas satélite de la Vía Láctea ........................................................25 1.3.1 Disco de satélites de la Vía Láctea (DoS) .............................................28 1.3.2 Hipótesis de formación del disco de galaxias (DoS) ...............................30 2. Marco teórico ............................................................................................. 35 2.1 Componentes de una galaxia de disco .............................................................35 2.1.1 Bulbo central ........................................................................................36 2.1.2 Disco ....................................................................................................36 2.1.3 Halo estelar ..........................................................................................36 2.1.4 Halo de materia oscura .........................................................................36 2.2 Modelos teóricos para el potencial gravitacional de las estructuras (Bulbo, Disco y Halo de materia oscura) ................................................................................37 2.2.1 Potencial de Hernquist (Bulbo central) ................................................37 XII Colisión de dos Galaxias de Disco 2.2.2 Perfil de densidad (Disco) .................................................................... 38 2.2.3 Potencial de Hernquist (Halo de materia oscura) ................................. 39 2.3 Orbita pre-colisión .......................................................................................... 40 2.3.1 Parámetro de impacto .......................................................................... 41 2.4 Colisión de galaxias ........................................................................................ 42 2.4.1 Sistemas no colisiónales ........................................................................ 42 2.4.2 Sistemas estelares interactuantes (definiciones) .................................... 43 2.4.3 Encuentro de galaxias en rotación ........................................................ 44 2.4.4 Encuentros de discos planos (estabilidad) ............................................ 46 2.4.5 Fricción dinámica ................................................................................. 48 2.4.6 Algunas colisiones reales y simulación .................................................. 48 3. Condiciones iniciales ................................................................................... 51 3.1 Software Zeno ................................................................................................. 51 3.2 Parámetros de la Vía Láctea........................................................................... 52 3.2.1 Condiciones iniciales baja resolución Vía Láctea .................................. 53 3.2.2 Condiciones iniciales alta resolución Vía Láctea ................................... 54 3.2.3 Masa del halo de materia oscura .......................................................... 55 3.3 Galaxias satélites ............................................................................................ 56 3.3.1 Redimensionamiento
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