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On the evolution of the Hubble constant through Supernovae Ia, Baryon Acoustic Oscillations: new perspectives on the GRB-cosmology

Presentation #202.14 in the session Cosmology — iPoster Session.

Published onJun 29, 2022
On the evolution of the Hubble constant through Supernovae Ia, Baryon Acoustic Oscillations: new perspectives on the GRB-cosmology

The Hubble constant (H0) tension, namely difference from 4 to 6 σ between the H0 value observed with Cepheids and Supernovae Ia (SNe Ia) and the one from Cosmic Microwave Background (CMB) still challenges the astrophysics and cosmology community. Previous analysis has shown that there is an evolution in the Hubble constant that scales as f(z) = H0/(1 + z)η, where H0 is H0(z = 0) and η is the evolutionary parameter. Here, we investigate if this evolution still holds by using the SNe Ia gathered in the Pantheon sample and the Baryon Acoustic Oscillations. We assume H0 = 70 km s-1 Mpc-1 as the local value and divide the Pantheon into three redshift-ordered bins. Similar to our previous analysis but varying two cosmological parameters contemporaneously (H0, Ω0m in the ΛCDM model and H0, wa in the w0waCDM model) and adding the Baryon Acoustic Oscillations, for each bin we implement a Markov-Chain Monte Carlo analysis (MCMC) obtaining the value of H0 assuming Gaussian priors to restrict the parameters spaces to values we expect and to avoid phantom Dark Energy models with w < -1. Subsequently, the values of H0 are fitted with the model f(z). Our results show that a decreasing trend with η ~ 10-2 is still visible in this sample. The η coefficient reaches zero in 2.0 σ for the ΛCDM model up to 5.8 σ for w0waCDM model. This trend, if not due to statistical fluctuations, could be explained through a hidden astrophysical bias, such as the effect of stretch evolution, or it requires new theoretical models, a possible proposition being the modified gravity theories, f(R). This work is a preparatory to understand how the combined probes still show an evolution of the H0 by redshift and what is the current status of simulations on GRB cosmology to obtain the uncertainties on the Ω0m comparable with the ones achieved through SNe Ia.

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