Calibration of extragalactic distances on different metallicity environments

In this work the distances to NGC 247, M33, IC 1613 and NGC 55 were found using Henrietta Leavitt's Period-Luminosity Relation (PLR) in the \textit{VIJK} filters in order to see if the galaxies' metallicity affected their distance calculus. This has been a long debated topic and the results will determine if the PLR is universal, which is relevant for the Cepheid extragalactic distance scale. The relations were calculated using an \textit{MM}-estimator, since this kind of robust regression deals with the heteroscedasticity problems present in astronomical data and allows the inclusion of influential points. The PLRs were also calculated using the slope of the Large Magellanic Cloud's PLR, since it is considered the zero point of this relation. Two distance moduli were used for the LMC: ($18.5 \pm 0.1$) mag found by Freedman et al. (2001) and ($18.477 \pm 0.004$) mag calculated by Pietrzy\'nski et al. (2019). Hence, for each galaxy two distances and an excess color were found. Comparing these results with the ones reported by the Araucaria project for the same galaxies, it was concluded that the excess colors found in this thesis are evidence of the non universality of the PLR, since the values with more discrepancy correspond to the galaxies with a significantly different metallicity than the LMC. This shows that the metallicity affects the slope of the PLR and that this distance calculus method only works correctly for galaxies with a similar metallicity to the LMC

• Autores: Cardona Rocha, Juanita
• Tipo de recurso: Trabajo de grado de pregrado
• Fecha de publicación: 2020
• Institución: Universidad de los Andes
• Repositorio: Séneca: repositorio Uniandes
• Idioma: eng
• OAI Identifier: oai:repositorio.uniandes.edu.co:1992/48780
• Acceso en línea: http://hdl.handle.net/1992/48780
• Palabra clave: Cefeidas (Astronomía); Estrellas pulsátiles; Estrellas supergigantes; Metalicidad; Astrofísica; Física
• Rights: openAccess
• License: http://creativecommons.org/licenses/by-nc-sa/4.0/