Structure, kinematics and metallicity of the Galactic Bulge
In the last few years evidence has been growing that the structure of the Galactic Bulge is very complex. Several independent studies suggest the presence of more than one stellar populations in the bulge, with different origins and a relative fraction changing across the bulge area. To characterize...
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| Tipo de recurso: | tesis doctoral |
| Estado: | Versión publicada |
| Fecha de publicación: | 2017 |
| País: | Chile |
| OAI Identifier: | oai:repositorio.anid.cl:10533/232961 |
| Acceso en línea: | https://hdl.handle.net/10533/232961 |
| Access Level: | acceso abierto |
| Palabra clave: | Ciencias Naturales Ciencias Físicas Astronomía |
| Sumario: | In the last few years evidence has been growing that the structure of the Galactic Bulge is very complex. Several independent studies suggest the presence of more than one stellar populations in the bulge, with different origins and a relative fraction changing across the bulge area. To characterize this stellar components, and the Milky Way Bulge itself, wide and large sample surveys are needed. In the last decade several studies has been done in order to access the bulge area, but the crowding and high extinction have prevented the systematic study of the inner Galactic bulge. In the present work the reader will find the main results obtained from the Giraffe Inner Bulge Survey (GIBS), which studied the red clump stars located inside 31 fields, confined in the area defined by the VVV survey (-10 < l < +10, -10 < b < +5). This survey can be divided in two branch according to the resolution used. The present work is advocated to the low-resolution setup, which used the LR8 grating of the FLAMES-GIRAFFE spectrograph at VLT. This setup provide spectra with a mean resolution of R 6500, centred around the calcium II triplet (CaT) features located at 8500 Angstroms. The three lines of the CaT were used to determine radial velocities and metallicities from a proper CaT metallicity calibration, based on calcium equivalent width measurements. The analysis of the data provide new kinematical and chemical information of the inner bulge, which support previous findings and extend them to fields as close to the galactic plane as b = -2 and b = -1 for the first time. Particularly, the information obtained allow us to clearly identify two main stellar components inside the galactic bulge, which do not follow the same spatial distribution. Contrary to expectations from previous works, we found the metal poor population to be more centrally concentrated than the metal rich one, and with a more axisymmetric spatial distribution. The metal rich population, on the other hand, is arranged in a boxy distribution, consistent with an edge-on bar. Together with this, a change in the metallicty gradient was found in the inner bulge (b < -3.5 degrees) with respect to the gradient observed in the outer bulge. As a direct product of this study, we provide kinematical and chemical maps obtained from the interpolation of the analysed grid. This maps and the observations provides new observational constraints on the actual chemodynamical properties of the Galactic bulge, that will help to discriminate between different formation models. |
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