Strong Progenitor Age-bias in Supernova Cosmology. II. Alignment with DESI BAO and Signs of a Non-Accelerating Universe

Junhyuk Son, Young-Wook Lee, Chul Chung, Seunghyun Park and Hyejeon Cho

ABSTRACT

Supernova (SN) cosmology is based on the key assumption that the luminosity standardization process of Type Ia SNe remainsinvariant with progenitor age. However, direct and extensive age measurements of SN host galaxies reveal a significant (5.5?)correlation between standardized SN magnitude and progenitor age, which is expected to introduce a serious systematic bias withredshift in SN cosmology. This systematic bias is largely uncorrected by the commonly used mass-step correction, as progenitorage and host galaxy mass evolve very differently with redshift. After correcting for this age-bias as a function of redshift, the SNdataset aligns more closely with the ?0??CDM model recently suggested by the DESI BAO project from a combined analysisusing only BAO and CMB data. This result is further supported by an evolution-free test that uses only SNe from young, coevalhost galaxies across the full redshift range. When the three cosmological probes (SNe, BAO, CMB) are combined, we find asignificantly stronger (> 9?) tension with the ΛCDM model than that reported in the DESI papers, suggesting a time-varyingdark energy equation of state in a currently non-accelerating universe.

MNRAS