Measurements of the characteristic length scale $$r_s$$ r s of the baryon acoustic oscillations (BAO) provide a robust determination of the distance-redshift relation. Currently, the best (sub-per cent) estimate of $$r_s$$ r s at the drag epoch is provided by Cosmic Microwave Background (CMB) observations assuming the validity of the standard $$\Lambda $$ Λ CDM model at $$z \sim 1000$$ z ∼ 1000 . Therefore, inferring $$r_s$$ r s from low-z observations in a model-independent way and comparing its value with CMB estimates provides a consistency test of the standard cosmology and its assumptions at high-z. In this paper, we address this question and estimate the absolute BAO scale combining angular BAO measurements and type Ia Supernovae data. Our analysis uses two different methods to connect these data sets and finds a good agreement between the low-z estimates of $$r_{s}$$ r s with the CMB sound horizon at drag epoch, regardless of the value of the Hubble constant $$H_0$$ H 0 considered. These results highlight the robustness of the standard cosmology at the same time that they also reinforce the need for more precise cosmological observations at low-z.
Fast Radio Bursts (FRBs) are millisecond-duration radio transients with an observed dispersion measure (DM) greater than the expected Milky Way contribution, which suggests that such events are of extragalactic origin. Although some models have been proposed to explain the physics of the pulse, the mechanism behind the FRBs emission is still unknown. From FRBs data with known host galaxies, the redshift is directly measured and can be combined with estimates of the DM to constrain the cosmological parameters, such as the baryon number density and the Hubble constant. However, the poor knowledge of the fraction of baryonic mass in the intergalactic medium ($$f_{IGM}$$ f IGM ) and its degeneracy with the cosmological parameters impose limits on the cosmological application of FRBs. In this work we present a cosmological model-independent method to determine the evolution of $$f_{IGM}$$ f IGM combining the latest FRBs observations with localized host galaxy and current supernovae data. We consider constant and time-dependent $$f_{IGM}$$ f IGM parameterizations and show, through a Bayesian model selection analysis, that a conclusive answer about the time-evolution of $$f_{IGM}$$ f IGM depend strongly on the DM fluctuations due to the spatial variation in cosmic electron density ($$\delta $$ δ ). In particular, our analysis show that the evidence varies from strong (in favor of a growing evolution of $$f_{IGM}$$ f IGM with redshift) to inconclusive, as larger values of $$\delta $$ δ are considered.
Fast Radio Bursts (FRBs) are millisecond-duration radio transients with an observed dispersion measure (DM) greater than the expected Milky Way contribution, which suggests that such events are of extragalactic origin. Although some models have been proposed to explain the physics of the pulse, the mechanism behind the FRBs emission still unknown. From FRBs data with known host galaxies, the redshift is directly measured and can be combined with estimates of the DM to constrain the cosmological parameters, such as the baryon number density and the Hubble constant. However, the poor knowledge of the fraction of baryonic mass in the intergalactic medium ( f IGM ) and its degeneracy with the cosmological parameters impose limits on the cosmological application of FRBs. In this work we present a model-independent method to determine the evolution of f IGM , combining the latest FRBs observations with localized host galaxy and current supernovae data. In our analysis we consider constant and time-dependent f IGM parameterizations and show, through a Bayesian model selection analysis, that there is a strong evidence in favor of a growing evolution of f IGM with redshift.
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