A New Master Supernovae Ia sample and the investigation of the H0 tension

by Maria Giovanna Dainotti (National Astronomical Observatory of Japan)

Tuesday 4 Feb 2025, 16:00 → 18:00 Europe/Rome

Aula Conversi (Dip. di Fisica - Edificio G. Marconi)

Modern cosmological research still thoroughly debates the discrepancy between local probes and the Cosmic Microwave Background observations in the Hubble constant (
H0 ) measurements, ranging from  4σ  to 6σ. In the current study we examine this tension using the Supernovae Ia (SNe Ia) data from the Pantheon, PantheonPlus, Joint Lightcurve Analysis (JLA), and Dark Energy Survey (DES) catalogs together with their combination called Master Sample containing 3789 SNe Ia, and dividing all of them into redshift-ordered bins. Two main binning techniques are presented: the equipopulation and the equispace in the logz. We perform a Markov-Chain Monte Carlo analysis (MCMC) for each bin to determine the H0  value, estimating it within the standard flat ΛCDM and the w0waCDM models. These H0 values are then fitted with the following phenomenological function: H0(z)=H0^/(1+z)^α, where H0^ is a free parameter representing H0(z) fitted at z=0 and α is the evolutionary parameter. Our results indicate a decreasing trend characterized by α∼0.01  whose consistency with zero range from 
1.00σ  at 3 bins in the Pantheon sample with the w0waCDM model to >6σ  at 12 bins with the JLA and DES samples within the ΛCDM model. Such a trend in the SNe Ia catalogs could be due to evolution with redshift for the SNe Ia astrophysical variables or unveiled selection biases. Alternatively, intrinsic physics, possibly the f(R)  theory of gravity, could be responsible for this trend. I will also explore possibility with combining Gamma-Ray Bursts, BAO and SNe Ia with a new likelihood analysis and without binning the data.