Time Dilation in Type Ia Supernova Spectra at High Redshift

TL;DR

This study confirms the time dilation effect in high-redshift Type Ia supernova spectra, supporting the expanding universe model and ruling out alternative hypotheses like tired light.

Contribution

It provides empirical spectral evidence for time dilation in supernovae, validating cosmological expansion predictions and testing alternative models.

Findings

Spectral aging rates match the 1/(1+z) expansion prediction.

Results exclude non-expanding universe models like tired light.

Supports the standard cosmological model with empirical data.

Abstract

We present multiepoch spectra of 13 high-redshift Type Ia supernovae (SNe Ia) drawn from the literature, the ESSENCE and SNLS projects, and our own separate dedicated program on the ESO Very Large Telescope. We use the Supernova Identification (SNID) code of Blondin & Tonry to determine the spectral ages in the supernova rest frame. Comparison with the observed elapsed time yields an apparent aging rate consistent with the 1/(1+z) factor (where z is the redshift) expected in a homogeneous, isotropic, expanding universe. These measurements thus confirm the expansion hypothesis, while unambiguously excluding models that predict no time dilation, such as Zwicky's "tired light" hypothesis. We also test for power-law dependencies of the aging rate on redshift. The best-fit exponent for these models is consistent with the expected 1/(1+z) factor.