Examining the Hubble tension with differences in supernova and host galaxies properties

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The persistent 4–6σ discrepancy between early- and late-time measurements of the Hubble constant ( ) is known as the "Hubble tension" and represents one of the major open problems in modern cosmology. In this work, we investigate how differences in light-curve parameters ( , ) and host galaxy properties ( e sSFR) between the calibration and Hubble Flow (HF) Type Ia supernova (SN Ia) samples affect the SN luminosity standardization and the estimation.

To do that, we generate subsamples from both samples and use them to estimate , , α, β, and . Both one- and multi-dimensional Kolmogorov–Smirnov tests are used to evaluate the consistency between the subsamples property distributions and analyze how the estimated parameters vary with the better matching of the subsamples. We find that the calibration sample is not fully representative of the HF sample, particularly in and sSFR. Improving consistency between subsamples leads to significant trends in , , α and , although overall values remain broadly stable.

More consistent subsamples also tend to produce a mass step consistent with zero within 1σ. We also try to disentangle SN subpopulations using different approaches, identifying consistent differences in ( 2–3σ) and ( 2σ), estimated using low- and high-stretch SN subpopulations, likely due to variations in dust properties and intrinsic color that are not captured by the standard β parameter. This results also suggest that the underlying SN subpopulations might contribute to additional dispersion in estimates.