THE PHYSICAL AND KINEMATICAL STRUCTURE OF MASSIVE AND DENSE COLD CORES
In spite of the efforts focused on understanding the formation of high mass stars, we do not have a clear understanding of which are the processes involved. To understand it, we need to characterize objects in very early stages of evolution and therefore infer the initial conditions of these process...
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| Tipo de recurso: | tesis doctoral |
| Estado: | Versión publicada |
| Fecha de publicación: | 2019 |
| País: | Chile |
| OAI Identifier: | oai:repositorio.anid.cl:10533/235755 |
| Acceso en línea: | https://hdl.handle.net/10533/235755 |
| Access Level: | acceso abierto |
| Palabra clave: | Ciencias Naturales Ciencias Físicas Astronomía |
| Sumario: | In spite of the efforts focused on understanding the formation of high mass stars, we do not have a clear understanding of which are the processes involved. To understand it, we need to characterize objects in very early stages of evolution and therefore infer the initial conditions of these processes. In this thesis, we study these objects from two different perspectives. First, we characterized four cold, dense, and massive clumps in the early stages of evolution (G305.136+0.068, G333.125- 0.562, G18.606-0.076, and G34.458+0.121), and we analyzed which are their collapse signatures. This was done using data from the Atacama Pathfinder Experiment (APEX) with an angular resolution of ∼20”. On the other hand, we studied the mass distribution within the quieter object (G305.136+0.068) using data from the Atacama Large Millimeter/submillimeter Array (ALMA) with high angular resolution (∼2”), being able to detect the small fragments that will become star seeds. The four objects observed with APEX show various kinematical characteristics showing different stages of evolution. In all the objects the molecular line velocity dispersions are broader than the thermal widths implying other types of processes like turbulence and/or collapse. The viral analysis of the objects indicates that they are likely to be bound. For two of the studied objects (G305.136+0.068, and G333.125-0.562), we found clear collapse signatures in the molecular line profiles. Regarding the ALMA observations towards G305.136+0.069, the dust continuum observations reveal the presence of twelve compact structures (cores) with masses ranging from 3.3 to 50.6 M⊙ and radius from 1800 to 5300 AU. The line observations indicate that the fragments are dominated by non-thermal motions. The virial parameters of the three most massive cores suggest that they are undergoing collapse. We find that in the regime of masses probed by our observations (M > 3 M⊙) the shape of the core mass function shows an overpopulation of high mass cores. |
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