“COSMOGRAFIA - DETERMINAÇÃO DE PARÂMETROS COSMOLÓGICOS A PARTIR DE SUPERNOVA IA E DO PARÂMETRO DE HUBBLE”

Abstract

In 1970 the cosmologist Allan Sandage described Cosmology as ” the search for two numbers”, referring to the Hubble parameter H0 and the deceleration parameter q0 [1]. Cosmography is a useful tool to test models and estimate these parameters as it is a kinematics approach of Cosmology. The first goal of this study is to estimate the parameters H0 , q0 e j0 using type Ia supernovae data and relate them to the ΛCDM model. The second goal is to study different parametrizations of the deceleration parameter q(z) using type Ia supernovae and cosmic chronometers data. With this, we can estimate q0 , H(z) e dL (z). It is also possible to calculate the equation of state parameter in the wCDM model and estimate the transition redshift, when the Universe expansion turned from a decelerated to an accelerated one. The most significant results regarding the first goal were the ones with maximum redshift of zlim = 0, 7. In this regime, we obtained H0 = 74.38 ± 0.39, q0 = −0.69 ± 0.09 and j0 = 1.74 ± 0.79 and the cosmographic fit had a maximum percentage difference of 1% to the standard model. As for the second goal, the results of q(z) parametrizations indicated an accelerated expansion of the Universe in z = 0, with w0 concordant with the expected by the standard model. The model with the best fit to the data favored an accelerated expansion more recent than the one predicted by the concordance model.