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

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 $0.1lesssim zlesssim 1.2$. 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 $Delta t_{
m em}$, and parametrizing the observed duration as $Delta t_{
m obs}=Delta t_{
m em}(1+z)^b$, 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 $b=1.003pm 0.005$ (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.

White, R., Davis, T. M., Lewis, G. F., Brout, D., Galbany, L., Glazebrook, K., ... Weaverdyck, N.

White, RMT||Davis, TM||Lewis, GF||Brout, D||Galbany, L||Glazebrook, K||Hinton, SR||Lee, J||Lidman, C||Möller, A||Sako, M||Scolnic, D||Smith, M||Sullivan, M||Sánchez, BO||Shah, P||Vincenzi, M||Wiseman, P||Abbott, TMC||Aguena, M||Allam, S||Andrade-Oliveira, F||Asorey, J||Bacon, D||Bocquet, S||Brooks, D||Buckley-Geer, E||Burke, DL||Rosell, A Carnero||Carollo, D||Carretero, J||da Costa, LN||Pereira, MES||De Vicente, J||Desai, S||Diehl, HT||Everett, S||Ferrero, I||Flaugher, B||Frieman, J||García-Bellido, J||Gaztanaga, E||Giannini, G||Gruendl, RA||Hollowood, DL||Honscheid, K||James, DJ||Kessler, R||Kuehn, K||Lahav, O||Lee, S||Lima, M||Marshall, JL||Mena-Fernández, J||Miquel, R||Myles, J||Nichol, RC||Ogando, RLC||Palmese, A||Pieres, A||Malagón, AA Plazas||Romer, AK||Sanchez, E||Cid, D Sanchez||Schubnell, M||Suchyta, E||Tarle, G||Tucker, BE||Walker, AR||Weaverdyck, N

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