OSCILAÇÕES ACÚSTICAS BARIÔNICAS NAS DISTRIBUIÇÕES DE QUASARES E GALÁXIAS AZUIS

Abstract

Abstract The large scale structure of the Universe has been studied at several redshifts using different cosmic tracers. Among the methods employed, the search for the signature of the baryon acoustic oscillations (BAO) is a powerful one because it can be used as a standard ruler. This acoustic oscillations, generated during the primordial Universe, left imprints in the distribution of matter, regions with slightly larger probability to form structures. To identify these signatures at different epochs serves to probe how the Universe evolves and its contents. We used BAO to characterize the Universe, extracting them from two different cosmic tracers, the quasars and blue galaxies from Sloan Digital Sky Survey. In the quasars case, located at high redshift with z ≥ 2, using a model-independent approach, we measure the transversal signal using the two-point angular correlation function tool (2PACF). For this, we select the data inside a thin redshift shell in the interval z ∈ [2.2, 2.25] and found the scale θ BAO = 1.77° ±0.31° with a statistical significance of 2.12σ. Additionally, we restrict the parameters for the models wCDM (Ωₘ and w₀) and w(t)CDM (w₀ and wₐ), and find that both show agreement with the concordance model ΛCDM. Besides that, using the three-point angular correlation function applied to the quasar catalogue, we confirm the signal measured at z = 2.225, with a statistical significance of 2.9σ. The triplets configuration used has sides θ₁ = 1.0° and θ₂ = 1.5° , with the third side varying in the range θ₃ ∈ [0.5° , 2.5° ]. The signal was detected at θ_BAO = 1.82° ± 0.21°. In the blue galaxies case, located at low redshifts with z ≤ 0.2, the analysis was splited into two parts. First, we use the 2PACF applied to a redshift shell z ∈ [0.105, 0.115], detecting the transversal signal at 19.8° ±3.26° with a statistical significance of 2.2σ. Then, in the second part, a tridimensional analysis was done using the two-point correlation function applied to the dataset in the interval z ∈ [0.05, 0.2] based on the cosmography approach to calculate distances, where the sound horizon scale rₛ = 100.7 ± 3.6 Mpc/h was detected. Using these results we determine the angular diameter distance D_A(0.11) = 262.52 ± 9.5 Mpc/h. Finally, adding this transversal BAO measurement to the quasar and other 13 measurements available in the literature obtained from luminous red galaxies we restrict the parameters for the models ΛCDM, wCDM and w(t)CDM. The results are compatible with the ΛCDM model. Key-words: baryon acoustic oscillations; large scale structure; quasars; blue galaxies.