Environmental dependence of Type Ia supernova standardisation on the local luminosity-weighted age
Year: 2026
Type: article
Abstract: Context. The dependence of the Type Ia supernova (SN Ia) standardised luminosity on host galaxy properties is a major source of uncertainty in cosmology. As next-generation surveys like LSST and HLTDS reduce statistical uncertainties, cosmological precision will be dominated by astrophysical systematic errors. However, the widely used empirical mass step, acting as an indirect global proxy, obscures the direct physical link to the progenitor’s environment, thereby potentially limiting the precision of SN Ia luminosity standardisation. Aims. We test whether the local luminosity-weighted age (LWA), used here as a statistical proxy for the age of the stellar population associated with SN Ia progenitors, is more closely related to the physical driver of standardised-luminosity variations than host galaxy mass. Methods. Using SDSS-MaNGA Pipe3D, we extracted the local LWA within a 1 kpc aperture for 56 SNe Ia and performed a joint likelihood analysis to disentangle the impacts of local age and mass on Hubble residuals. Results. We find that SNe Ia in younger environments are significantly fainter than those in older ones, exhibiting a step amplitude of 0.163 mag (5.2 σ ) after standardisation. While global and local mass steps are initially observed (0.071 mag, 2.0 σ and 0.087 mag, 2.4 σ , respectively), both become statistically insignificant when fitting for age and mass simultaneously: the global mass step decreases to 0.028 mag (0.9 σ ), while the corresponding age step remains robust at 0.156 mag (4.9 σ ). Similarly, the local mass step becomes statistically insignificant (0.012 mag, 0.3 σ ), whereas the age step persists at 0.157 mag (4.4 σ ). Furthermore, the weighted Hubble residual decreases from 0.1550 to 0.1376 mag after the local LWA step is introduced. Conclusions. Our results provide evidence that the mass step is substantially reduced when the local LWA is included. Furthermore, the inferred dark energy equation of state parameter ( w ) could be affected by the treatment of the local LWA, highlighting the potential importance of environmental effects for next-generation SN Ia cosmology.
Source: Astronomy and Astrophysics
Language: English
Subfield: Astronomy and Astrophysics
Field: Physics and Astronomy
Domain: Physical Sciences
Open Access status: gold
Estimated APC paid: $1,865
OpenAlex ID: W7212248018