A cosmology-independent calibration of type Ia supernovae data

TL;DR

This paper develops a method to calibrate type Ia supernovae data without assuming a specific cosmological model, confirming previous results and supporting the validity of existing cosmological analyses.

Contribution

It introduces a cosmology-independent calibration approach for SNe Ia data, demonstrating its consistency with traditional model-dependent methods.

Findings

Calibration corrections are similar to those from ΛCDM-based methods.

Cosmology-independent standardisation does not alter previous model comparison results.

Method is applicable to smaller supernova samples like superluminous type Ic supernovae.

Abstract

Recently, the common methodology used to transform type Ia supernovae (SNe Ia) into genuine standard candles has been suffering criticism. Indeed, it assumes a particular cosmological model (namely the flat $\Lambda$CDM) to calibrate the standardisation corrections parameters, i.e. the dependency of the supernova peak absolute magnitude on its colour, post-maximum decline rate and host galaxy mass. As a result, this assumption could make the data compliant to the assumed cosmology and thus nullify all works previously conducted on model comparison. In this work, we verify the viability of these hypotheses by developing a cosmology-independent approach to standardise SNe Ia data from the recent JLA compilation. Our resulting corrections turn out to be very close to the $\Lambda$CDM-based corrections. Therefore, even if a $\Lambda$CDM-based calibration is questionable from a theoretical point of view, the potential compliance of SNe Ia data does not happen in practice for the JLA compilation. Previous works of model comparison based on these data do not have to be called into question. However, as this cosmology-independent standardisation method has the same degree of complexity than the model-dependent one, it is worth using it in future works, especially if smaller samples are considered, such as the superluminous type Ic supernovae.