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Sample variance in the local measurements of the Hubble constant

Wu, Hao-Yi and Huterer, Dragan (2017) Sample variance in the local measurements of the Hubble constant. Monthly Notices of the Royal Astronomical Society, 471 (4). pp. 4946-4955. ISSN 0035-8711.

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The current >3σ tension between the Hubble constant H0 measured from local distance indicators and from cosmic microwave background is one of the most highly debated issues in cosmology, as it possibly indicates new physics or unknown systematics. In this work, we explore whether this tension can be alleviated by the sample variance in the local measurements, which use a small fraction of the Hubble volume. We use a large-volume cosmological N-body simulation to model the local measurements and to quantify the variance due to local density fluctuations and sample selection. We explicitly take into account the inhomogeneous spatial distribution of type Ia supernovae. Despite the faithful modelling of the observations, our results confirm previous findings that sample variance in the local Hubble constant (H^(loc)_0) measurements is small; we find σ(H^(loc)_0) = 0.31km s^(-1)Mpc^(-1), a nearly negligible fraction of the ∼6 km s^(−1)Mpc^(−1) necessary to explain the difference between the local and global H0 measurements. While the H_0 tension could in principle be explained by our local neighbourhood being a underdense region of radius ∼150 Mpc, the extreme required underdensity of such a void (δ ≃ −0.8) makes it very unlikely in a ΛCDM universe, and it also violates existing observational constraints. Therefore, sample variance in a ΛCDM universe cannot appreciably alleviate the tension in H0 measurements even after taking into account the inhomogeneous selection of type Ia supernovae.

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Additional Information:© 2017 The Authors Published by Oxford University Press on behalf of the Royal Astronomical Society. Accepted 2017 July 28. Received 2017 July 28; in original form 2017 June 28. Published: 02 August 2017. We thank Adam Riess, Dan Shafer and Radek Wojtak for insightful suggestions, Matt Turk for assistance for accessing the Dark Sky simulations, and Dan Scolnic for providing the Supercal data set. HW acknowledges the support by the U.S. National Science Foundation (NSF) grant AST1313037. DH is supported by NSF under contract AST-0807564 and the Department of Energy under contract DE-FG02-95ER40899. The calculations in this work were performed on the Caltech computer cluster Zwicky, which is supported by NSF MRI-R2 award number PHY-096029, and on kingjames, lovingly supported by his majesty's owner at the University of Michigan.
Funding AgencyGrant Number
Department of Energy (DOE)DE-FG02-95ER40899
Subject Keywords:methods: numerical – galaxies: haloes – cosmological parameters – large-scale structure of Universe – cosmology: theory
Record Number:CaltechAUTHORS:20171006-080606803
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Official Citation:Hao-Yi Wu, Dragan Huterer; Sample variance in the local measurements of the Hubble constant, Monthly Notices of the Royal Astronomical Society, Volume 471, Issue 4, 11 November 2017, Pages 4946–4955,
Usage Policy:No commercial reproduction, distribution, display or performance rights in this work are provided.
ID Code:82147
Deposited By: Tony Diaz
Deposited On:06 Oct 2017 16:27
Last Modified:06 Oct 2017 16:27

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