A Hubble constant estimate from galaxy cluster and type Ia SNe observations
Abstract: In this work, we constrain the Hubble constant parameter, H 0, using a combination of the Pantheon sample and galaxy clusters (GC) measurements from minimal cosmological assumptions. Assuming the validity of the cosmic distance duality relation, an estimator is created for H 0 that only depends on simple geometrical distances, which is evaluated from Pantheon and a GC angular diameter distance sample afterward. The statistical and systematic errors in GC measuremen… Show more
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References 90 publications
Reconstructing the growth index $$\gamma $$ with Gaussian processes
Alternative cosmological models have been proposed to alleviate the tensions reported in the concordance cosmological model, or to explain the current accelerated phase of the universe. One way to distinguish between General Relativity and modified gravity models is using current astronomical data to measure the growth index $$\gamma $$ γ , a parameter related to the growth of matter perturbations, which behaves differently in different metric theories. We propose a model independent methodology for determining $$\gamma $$ γ , where our analyses combine diverse cosmological data sets, namely $$\{ f(z_i) \}$$ { f ( z i ) } , $$\{ [f\sigma _8](z_i) \}$$ { [ f σ 8 ] ( z i ) } , and $$\{ H(z_i) \}$$ { H ( z i ) } , and use Gaussian Processes, a non-parametric approach suitable to reconstruct functions. This methodology is a new consistency test for $$\gamma $$ γ constant. Our results show that, for the redshift interval $$0< z < 1$$ 0 < z < 1 , $$\gamma $$ γ is consistent with the constant value $$\gamma = 0.55$$ γ = 0.55 , expected in General Relativity theory, within $$2 \sigma $$ 2 σ confidence level (CL). Moreover, we find $$\gamma (z=0)$$ γ ( z = 0 ) = 0.311 $$\pm 0.144 $$ ± 0.144 and $$\gamma (z=0) = 0.609 \pm 0.200$$ γ ( z = 0 ) = 0.609 ± 0.200 for the reconstructions using the $$\{ f(z_i) \}$$ { f ( z i ) } and $$\{ [f\sigma _8](z_i) \}$$ { [ f σ 8 ] ( z i ) } data sets, respectively, values that also agree at a 2$$\sigma $$ σ CL with $$\gamma = 0.55$$ γ = 0.55 . Our methodology and analyses can be considered as an alternative approach in light of the current discussion in the literature that suggests a possible evidence for the growth index evolution.
Reconstructing the growth index $$\gamma $$ with Gaussian processes
Alternative cosmological models have been proposed to alleviate the tensions reported in the concordance cosmological model, or to explain the current accelerated phase of the universe. One way to distinguish between General Relativity and modified gravity models is using current astronomical data to measure the growth index $$\gamma $$ γ , a parameter related to the growth of matter perturbations, which behaves differently in different metric theories. We propose a model independent methodology for determining $$\gamma $$ γ , where our analyses combine diverse cosmological data sets, namely $$\{ f(z_i) \}$$ { f ( z i ) } , $$\{ [f\sigma _8](z_i) \}$$ { [ f σ 8 ] ( z i ) } , and $$\{ H(z_i) \}$$ { H ( z i ) } , and use Gaussian Processes, a non-parametric approach suitable to reconstruct functions. This methodology is a new consistency test for $$\gamma $$ γ constant. Our results show that, for the redshift interval $$0< z < 1$$ 0 < z < 1 , $$\gamma $$ γ is consistent with the constant value $$\gamma = 0.55$$ γ = 0.55 , expected in General Relativity theory, within $$2 \sigma $$ 2 σ confidence level (CL). Moreover, we find $$\gamma (z=0)$$ γ ( z = 0 ) = 0.311 $$\pm 0.144 $$ ± 0.144 and $$\gamma (z=0) = 0.609 \pm 0.200$$ γ ( z = 0 ) = 0.609 ± 0.200 for the reconstructions using the $$\{ f(z_i) \}$$ { f ( z i ) } and $$\{ [f\sigma _8](z_i) \}$$ { [ f σ 8 ] ( z i ) } data sets, respectively, values that also agree at a 2$$\sigma $$ σ CL with $$\gamma = 0.55$$ γ = 0.55 . Our methodology and analyses can be considered as an alternative approach in light of the current discussion in the literature that suggests a possible evidence for the growth index evolution.
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