The Dark Energy Survey Supernova Program: slow supernovae show cosmological time dilation out to z ~ 1

• Published in: Monthly notices of the Royal Astronomical Society 2024-09, Vol.533 (3), p.3365-3378
• Main Authors: White, R M T, Davis, T M, Lewis, G F, Brout, D, Galbany, L, Glazebrook, K, Hinton, S R, Lee, J, Lidman, C, Möller, A, Sako, M, Scolnic, D, Smith, M, Sullivan, M, Sánchez, B O, Shah, P, Vincenzi, M, Wiseman, P, Abbott, T M C, Aguena, M, Allam, S, Andrade-Oliveira, F, Asorey, J, Bacon, D, Bocquet, S, Brooks, D, Buckley-Geer, E, Burke, D L, Rosell, A Carnero, Carollo, D, Carretero, J, da Costa, L N, Pereira, M E S, De Vicente, J, Desai, S, Diehl, H T, Everett, S, Ferrero, I, Flaugher, B, Frieman, J, García-Bellido, J, Gaztanaga, E, Giannini, G, Gruendl, R A, Hollowood, D L, Honscheid, K, James, D J, Kessler, R, Kuehn, K, Lahav, O, Lee, S, Lima, M, Marshall, J L, Mena-Fernández, J, Miquel, R, Myles, J, Nichol, R C, Ogando, R L C, Palmese, A, Pieres, A, Malagón, A A Plazas, Romer, A K, Sanchez, E, Cid, D Sanchez, Schubnell, M, Suchyta, E, Tarle, G, Tucker, B E, Walker, A R, Weaverdyck, N
• Format: Article
• Language: English
• Subjects: Astronomical models; ASTRONOMY AND ASTROPHYSICS; Cosmology; cosmology: observations; Dark energy; Light; Light curve; Red shift; Sky surveys (astronomy); Supernovae; supernovae: general; Time measurement
• ISSN: 0035-8711; 1365-2966
• DOI: 10.1093/mnras/stae2008

ABSTRACT We present a precise measurement of cosmological time dilation using the light curves of 1504 Type Ia supernovae from the Dark Energy Survey spanning a redshift range $0.1\lesssim z\lesssim 1.2$. We find that the width of supernova light curves is proportional to $(1+z)$, as expected for time dilation due to the expansion of the Universe. Assuming Type Ia supernovae light curves are emitted with a consistent duration $\Delta t_{\rm em}$, and parametrizing the observed duration as $\Delta t_{\rm obs}=\Delta t_{\rm em}(1+z)^b$, we fit for the form of time dilation using two methods. First, we find that a power of $b \approx 1$ minimizes the flux scatter in stacked subsamples of light curves across different redshifts. Secondly, we fit each target supernova to a stacked light curve (stacking all supernovae with observed bandpasses matching that of the target light curve) and find $b=1.003\pm 0.005$ (stat) $\pm \, 0.010$ (sys). Thanks to the large number of supernovae and large redshift-range of the sample, this analysis gives the most precise measurement of cosmological time dilation to date, ruling out any non-time-dilating cosmological models at very high significance.