Improving SNe Ia as distance indicators

Unlocking the mystery of dark energy is one of the key goals of observational cosmology. The LambdaCDM model, in which the dark energy equation-of-state parameter is exactly -1, has so far survived the enormous improvement in constraints achieved since the original discovery of the accelerating universe using type Ia supernovae (SNe Ia) as standard candles. However, recent results from the Dark Energy Survey (DES) and the Dark Energy Spectroscopic Instrument (DESI) are putting the LambdaCDM model under pressure [1,2]. Both experiments provide hints that dark energy varies with time.  If verified, this would rule out Einstein's cosmological constant as the reason for the accelerating universe

SNe Ia are not perfect distance indicators. Even after correcting their luminosities for the established correlations with SN colour and light curve width, there remains a correlation between distance residuals and the properties of the host galaxy.  The correlation is probably driven by the improper way the colour corrections are applied. If true, then there will also be a relation between the intrinsic properties of the SNe and residuals.

This project will search for correlations between the spectral properties of SNe Ia and residuals using the DEBASS - a new sample of 500 SNe Ia.  The aim is to use these correlations to improve SNe Ia as distance indicators and tighten constraints on dark energy.

The project consists of the following elements

- extracting properties fron SN spectra

- correlating these properties with residuals

- applying a correction to the distance estimates

The project is suitable for honours or masters students.

Refs:

[1] DES Collaboration et al. 2024,ApJ, 973, 14:

[2] DESI Collaboration et al. 2025, arXiV 2503.14738