• JoomlaWorks Simple Image Rotator
  • JoomlaWorks Simple Image Rotator
  • JoomlaWorks Simple Image Rotator
  • JoomlaWorks Simple Image Rotator
  • JoomlaWorks Simple Image Rotator
  • JoomlaWorks Simple Image Rotator
  • JoomlaWorks Simple Image Rotator
  • JoomlaWorks Simple Image Rotator
  • JoomlaWorks Simple Image Rotator
  • JoomlaWorks Simple Image Rotator
 
  Bookmark and Share
 
 
Master's Dissertation
DOI
https://doi.org/10.11606/D.14.2023.tde-16052023-140044
Document
Author
Full name
Fabricia Oliveira Barbosa
E-mail
Institute/School/College
Knowledge Area
Date of Defense
Published
São Paulo, 2023
Supervisor
Committee
Rossi, Silvia Cristina Fernandes (President)
Brito, Alan Alves
Pinto, Helio Jaques Rocha
Placco, Vinicius Moris
Title in Portuguese
Arqueologia Galáctica por meio das estrelas azuis do ramo horizontal
Keywords in Portuguese
Distâncias
Halo galáctico
Ramo horizontal
Abstract in Portuguese
Após o início da queima estável de hélio, estrelas de baixa massa apresentam luminosidades aproximadamente constantes e compõem o chamado "ramo horizontal". Essa característica permite que sejam utilizadas como velas-padrão e, dado que elas são brilhantes e podem ser encontradas a dezenas de quiloparsecs do Sol, são excelentes objetos para explorar as regiões mais externas da Galáxia. Este projeto tem como foco as estrelas azuis do ramo horizontal (BHBs), a população mais velha e pobre em metais nessa fase evolutiva. As BHBs foram selecionadas a partir do catálogo do Sloan Digital Sky Survey, que disponibiliza dados fotométricos e espectroscópicos. Foram encontradas cerca de 5700 BHBs com os critérios aplicados. A abordagem robusta utilizada permitiu atribuir probabilidades individuais para os estágios evolutivos das estrelas situadas na mesma faixa de cor, sendo vantajosa em comparação com as seleções de BHBs anteriores, as quais adotaram cortes log g simples. Suas distâncias foram inferidas a partir da magnitude absoluta, a qual foi obtida por meio de uma nova relação proposta em Barbosa et al. (2022). Com essa amostra, os gradiente de cor e idade observados no halo Galáctico foram revisitados. Os resultados são compatíveis com a literatura, com um gradiente de idade de ~ -65 Mano/kpc até 18 kpc e ~ -16 Mano/kpc entre ~ 18 e 47 kpc. Essa mudança nítida sugere que o halo foi formado pela incorporação de diferentes sistemas menores. Além disso, é possível identificar estruturas conhecidas na distribuição de idades, como a corrente de Sagitário e a nuvem Hércules-Áquila.
Title in English
Galactic archeology through blue horizontal-branch stars
Keywords in English
Distances
Galactic halo
Horizontal branch
Abstract in English
After the start of stable helium burning, low-mass stars present approximately constant luminosities and form the so-called "horizontal branch". This characteristic allows them to be used as standard candles and, as they are bright and can be found tens of kiloparsecs from the Sun, are excellent objects to explore the outermost regions of the Galaxy. This project focuses on blue horizontal-branch stars (BHBs), the oldest and metal-poor population in this evolutionary stage. The BHBs were selected from the Sloan Digital Sky Survey catalog, which provides photometric and spectroscopic data. About 5700 BHBs were found with the applied criteria. The robust approach used allowed assigning individual probabilities to the evolutionary stages of stars located in the same color range, which is advantageous compared to previous BHB selections that adopted simple log g cuts. Their distances were inferred from the absolute magnitude obtained from a new relation proposed by Barbosa et al. (2022). With this sample, the color and age gradients observed in the Galactic halo were revisited. The results are consistent with the literature, with an age gradient of ~ -65 Myr/kpc up to 18 kpc and ~ -16 Myr/kpc between ~ 18 and 47 kpc. This pronounced transition suggests that the halo was formed by the merger of different smaller systems. In addition, it is possible to identify known structures in the age distribution, such as the Sagittarius stream and the Hercules-Aquila cloud.
 
WARNING - Viewing this document is conditioned on your acceptance of the following terms of use:
This document is only for private use for research and teaching activities. Reproduction for commercial use is forbidden. This rights cover the whole data about this document as well as its contents. Any uses or copies of this document in whole or in part must include the author's name.
Dissertacao.pdf (7.89 Mbytes)
Publishing Date
2023-05-16
 
WARNING: Learn what derived works are clicking here.
All rights of the thesis/dissertation are from the authors
CeTI-SC/STI
Digital Library of Theses and Dissertations of USP. Copyright © 2001-2024. All rights reserved.