Tesis Doctoral
DOI
10.11606/T.14.2012.tde-30012013-113804
Documento
Autor
Nombre completo
Oscar Cavichia de Moraes
Dirección Electrónica
Área de Conocimiento
Fecha de Defensa
Publicación
São Paulo, 2012
Director
Tribunal
Costa, Roberto Dell' Aglio Dias da (Presidente)
Lepine, Jacques Raymond Daniel
Lorente, Mercedes Mollá
Maciel, Walter Junqueira
Pinto, Helio Jaques Rocha
Título en portugués
Populações e evolução do bojo e região central da Galáxia
Palabras clave en portugués
abundâncias químicas
espectroscopia
evolução química
nebulosas planetárias
Via Láctea
Resumen en portugués
Título en inglés
Populations and the evolution of the bulge and central region of the Galaxy
Palabras clave en inglés
bulge
chemical abundances
chemical evolution
disk
Milky Way
planetary nebulae
spectroscopy
Resumen en inglés
This project proposes a comprehensive approach to describe the evolution of the central region of the Galaxy, comprising the bulge, the bar and their interfaces with the inner disk and the central region of the halo. We intend to investigate the chemical and kinematic properties of these structures, which are interconnected, aiming to separate them and apply these results to a model for the formation and evolution of the bulge and inner disk, capable to describe simultaneously distinct aspects of the evolution of the central region of the Galaxy. First, a sample of planetary nebulae (PNe) located in the inner-disk and bulge of the Galaxy is used in order to find the galactocentric distance that better separates these two populations, from the point of view of abundances. Statistical distance scales were used to study the distribution of abundances across the disk-bulge interface. A Kolmogorov-Smirnov test was used to find the distance in which the chemical properties of these regions better separates. The results of the statistical analysis indicate that, on the average, the inner population has lower abundances than the outer. Additionally, for the $\alpha$-elements abundances, the inner population does not follow the disk radial gradient towards the galactic centre. Based on our results, we suggest a bulge-disk interface at 1.5 kpc, marking the transition between the bulge and inner-disk of the Galaxy, as defined by the intermediate mass population. Second, we present spectrophotometric observations for a sample of 21 PNe located towards the galactic centre of the Galaxy. The abundances are derived based on observations in the optical domain made at the SOAR telescope. Their location is interesting since there are no observations of PNe in this region. The data show lower oxygen abundances compared to those from PNe located in the inner disk and other bulge regions. The results show that the bulge has a complex composition of stellar populations. The presence of PNe with low abundances indicates that the bulge might be formed from an old galactic disk through secular evolution. On the other hand, other objects from our sample have abundances compared to those from inner disk PNe. This is evidence that two or more populations might compose the bulge: one originated from the thin disk, and the other from the thick disk. Last, we propose a chemical evolution model that includes radial gas flows. This is done in order to mimic the effects of the galactic bar on the chemical abundances distributions and the gas density profiles and the star formation rate (SFR). The results of the models with radial flows point to a high SFR in the bulge and, additionally, the SFR and gas density profiles in the inner Galaxy are better reproduced after the inclusion of radial gas flows in the model. After including a specific velocity pattern for the bar, the results show a flattening of the radial abundance gradient. Our results indicate that radial gas flows may play an important role in the star formation near the centre of barred spiral galaxies.

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Fecha de Publicación
2013-01-31

ADVERTENCIA: El material descrito abajo se refiere a los trabajos derivados de esta tesis o disertación. El contenido de estos documentos es responsabilidad del autor de la tesis o disertación.
• CAVICHIA, O., et al. The role of the Galactic bar in the chemical evolution of the Milky Way [doi:10.1093/mnras/stt2164]. Royal Astronomical Society. Monthly Notices [online], 2013, vol. in, p. press.
• CAVICHIA, O., COSTA, R. D. D., and MACIEL, W. J. Planetary nebulae in the inner Milky Way II: the Bulge-Disk transition. Revista Mexicana de Astronomía y Astrofísica, 2011, vol. 47, p. 49-61.
• CAVICHIA, O., COSTA, R. D. D., and MACIEL, W. J. Planetary nebulae in the inner Milky Way: new abundances. Revista Mexicana de Astronomía y Astrofísica, 2010, vol. 46, p. 159-177.
• Cavichia, Oscar, Costa, Roberto D. D., and Maciel, Walter J. Helium abundances in inner Galaxy planetary nebulae [doi:10.1017/S1743921310004035]. In IAU Symposium 268: Light Elements in the Universe, Genebra, 2009. Proceedings of the IAU Symposium 268.Cambridge : Cambridge University Press, 2009. Abstract.
• CAVICHIA, O., et al. Planetary nebulae and the chemical evolution of the galactic bulge: New abundances of older objects. In IAU Symposium 283, Puerto de la Cruz/Tenerife, 2011. Proceedings of the IAU Symposium 283: Planetary nebulae - an eye to the future.Cambridge : Cambridge Un. Press, 2012. Abstract. Available from: http://journals.cambridge.org/action/displayAbstract?fromPage=online&aid=8685741.
• CAVICHIA, O., et al. The star formation rate in the inner Milky Way Galaxy. In IAU Symposium 292 - Molecular gas, dust and star formation in galaxies, Beijing, 2012. Proceedings of the IAU Symposium 292.Cambridge : Cambridge Un Press, 2013. Abstract.
• CAVICHIA, O., and COSTA, R. D. D. The chemical evolution of the Milky Way with radial flows. In The Chemical Evolution of the Milky Way, Sesto Pusteria, 2012. The Chemical Evolution of the Milky Way.Sexten : Sexten Center for Astrophysics (SCfA), 2012. Available from: http://www.sexten-cfa.eu/public/2011/ChemEvo_Milky_way/Costa.pdf.
• Cavichia, Oscar, Costa, Roberto D. D., and Maciel, Walter J. Planetary nebulae in the inner Milky Way [doi:10.1017/S174392131000089X]. In IAU Symposium 265: Chemical Abundances in the Universe: Connecting First Stars to Planets, Rio de Janeiro. Proceedings of the IAU Symposium 265.Cambridge : Cambridge University Press, 2009. Abstract.
• COSTA, R. D. D., CAVICHIA, O., and MACIEL, W. J. Chemical abundances of planetary nebulae in the disk-bulge connection. In IAU Symposium 254: The Galaxy Disk in Cosmological Context, Copenhagen, 2009. Proceedings of the IAU Symposium 254.Cambridge : Cambridge University Press, 2009.
• COSTA, R. D. D., CAVICHIA, O., and MACIEL, W. J. Planetary nebulae and the determination of the bulge-disk border. In IAU Symposium 289, Pequim, 2012. Proceedings of the IAU Symposium 289: Advancing the physics of cosmic distances. : Cambridge Un. Press, 2012.
Todos los derechos de la tesis/disertación pertenecen a los autores
Centro de Informática de São Carlos