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2020ApJ...902...14S - Astrophys. J., 902, 14-14 (2020/October-2)

Effects of supernova redshift uncertainties on the determination of cosmological parameters.


Abstract (from CDS):

Redshifts used in current cosmological supernova samples are measured using two primary techniques, one based on well-measured host galaxy spectral lines and the other based on supernova-dominated spectra. Here, we construct an updated Pantheon catalog with revised redshifts, redshift sources, and estimated uncertainties for the entire sample to investigate whether these two techniques yield consistent results. The best-fit cosmological parameters using these two measurement techniques disagree, with a supernova-only sample producing Ωm 3.2σ higher and H0 2.5σ lower than a hostz-only sample, and we explore several possible sources of bias that could result from using the lower-precision supernova-dominated redshifts. In a pilot study, we show that using a host redshift-only subsample will generically produce lower Ωm and matter density Ωmh2 and slightly higher H0 than previous analysis which, for the Pantheon data set, could result in supernova and cosmic microwave background measurements agreeing on Ωmh2 despite tension in H0. To obtain rigorous results, though, the Pantheon catalog should be improved by obtaining host spectra for supernovae that have faded, and future surveys should be designed to use host galaxy redshifts rather than lower-precision methods.

Abstract Copyright: © 2020. The American Astronomical Society. All rights reserved.

Journal keyword(s): Cosmological parameters - Cosmology - Type Ia supernovae - Astronomy data analysis - Standard candles

VizieR on-line data: <Available at CDS (J/ApJ/902/14): table2.dat>

Simbad objects: 1047

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