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Robust and model-independent cosmological constraints from distance measurements

Zhai, Zhongxu and Wang, Yun (2019) Robust and model-independent cosmological constraints from distance measurements. Journal of Cosmology and Astroparticle Physics, 2019 (7). Art. No. JCAP07(2019)005. ISSN 1475-7516. doi:10.1088/1475-7516/2019/07/005.

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We present a systematic analysis of the cosmological constraints from the "Pantheon Sample" of 1048 Type Ia Supernovae (SNe Ia) in the redshift range 0.01<z<2.3 compiled by Scolnic et al. (2018). Applying the flux-averaging method for detecting unknown systematic effects, we find that the "Pantheon" sample has been well calibrated and the bias caused by unknown systematic errors has been minimized. We present the estimate of distances measured from SNe Ia and reconstruct the expansion history of the Universe. The results are in agreement with a simple cosmological constant model and reveals the possible improvements that future SN Ia observations from WFIRST and LSST can target. We have derived distance priors using the Cosmic Microwave Background (CMB) data from the Planck 2018 final data release, and combine them with SNe Ia and baryon acoustic oscillation (BAO) data, to explore the impact from the systematic errors of SNe Ia on the combined cosmological parameter constraints. Using the combined data set of SNe Ia, BAO, and CMB distance priors, we measure the dark energy density function X(z)=ρX(z)/ρX(0) as a free function (defined as a cubic spline of its values at z=0.33, 0.67, 1.0), along with the cosmological parameters (Ω_k, Ω_m, Ω_b, H_0). We find no deviation from a flat Universe dominated by a cosmological constant (X(z)=1), and H_0=68.4± 0.9 km s^(−1)Mpc^(−1), straddling the Planck team's measurement of H_0=67.4± 0.5 km s^(−1)Mpc^(−1), and Riess et al. (2018) measurement of H_0=73.52± 1.62 km s^(−1)Mpc^(−1). Adding H_0=73.52± 1.62 km s^(−1)Mpc^(−1) as a prior to the combined data set leads to the time dependence of the dark energy density at z~ 0.33 at 68% confidence level. Not including the systematic errors on SNe Ia has a similar but larger effect on the dark energy density measurement.

Item Type:Article
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URLURL TypeDescription Paper
Zhai, Zhongxu0000-0001-7984-5476
Additional Information:© 2019 IOP Publishing Ltd and Sissa Medialab. Accepted 19 June 2019; Published 1 July 2019. ZZ thanks Jeremy Tinker for helpful discussions and suggestions, and Savvas Nesseris for his comments. We acknowledge the use of the public softwares Matplotlib [53], NumPy [54], SciPy [55], and Emcee [56]. This work is supported in part by NASA grant 15-WFIRST15-0008, Cosmology with the High Latitude Survey WFIRST Science Investigation Team (SIT).
Group:Infrared Processing and Analysis Center (IPAC)
Funding AgencyGrant Number
Issue or Number:7
Record Number:CaltechAUTHORS:20190708-161418072
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Official Citation:Zhongxu Zhai and Yun Wang JCAP07(2019)005
Usage Policy:No commercial reproduction, distribution, display or performance rights in this work are provided.
ID Code:96931
Deposited By: Tony Diaz
Deposited On:08 Jul 2019 23:46
Last Modified:16 Nov 2021 17:24

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