Local Hole revisited: evidence for bulk motions and self-consistent outflow

Shanks, T; Hogarth, LM; Metcalfe, N; Whitbourn, J

doi:10.1093/mnras/stz2863

Local Hole revisited: evidence for bulk motions and self-consistent outflow

Shanks, T; Hogarth, LM; Metcalfe, N; Whitbourn, J

Authors

T Shanks

LM Hogarth

Dr Nigel Metcalfe nigel.metcalfe@durham.ac.uk
Assistant Professor

J Whitbourn

Abstract

We revisit our mapping of the ‘Local Hole’, a large underdensity in the local galaxy redshift distribution that extends out to redshift, z ≈ 0.05 and a potential source of outflows that may perturb the global expansion rate and thus help mitigate the present ‘H0 tension’. First, we compare local peculiar velocities measured via the galaxy average redshift-magnitude Hubble diagram, z¯¯¯(m)⁠, with a simple dynamical outflow model based on the average underdensity in the Local Hole. We find that this outflow model is in good agreement with our peculiar velocity measurements from z¯¯¯(m) and not significantly inconsistent with SNIa peculiar velocity measurements from at least the largest previous survey. This outflow could cause an ≈2 − 3% increase in the local value of Hubble’s constant. Second, considering anisotropic motions, we find that the addition of the outflow model may improve the z¯¯¯(m) fit of a bulk flow where galaxies are otherwise at rest in the Local Group frame. We conclude that the Local Hole plus neighbouring overdensities such as the Shapley Supercluster may cause outflow and bulk motions out to ≈150h−1Mpc that are cosmologically significant and that need to be taken into account in estimating Hubble’s constant.

Citation

Shanks, T., Hogarth, L., Metcalfe, N., & Whitbourn, J. (2019). Local Hole revisited: evidence for bulk motions and self-consistent outflow. Monthly Notices of the Royal Astronomical Society, 490(4), 4715-4720. https://doi.org/10.1093/mnras/stz2863

Journal Article Type	Article
Acceptance Date	Oct 6, 2019
Online Publication Date	Oct 14, 2019
Publication Date	Dec 31, 2019
Deposit Date	Oct 17, 2019
Publicly Available Date	Oct 17, 2019
Journal	Monthly Notices of the Royal Astronomical Society
Print ISSN	0035-8711
Electronic ISSN	1365-2966
Publisher	Royal Astronomical Society
Peer Reviewed	Peer Reviewed
Volume	490
Issue	4
Pages	4715-4720
DOI	https://doi.org/10.1093/mnras/stz2863

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Copyright Statement
This article has been accepted for publication in the Monthly notices of the Royal Astronomical Society ©: 2019 The Author(s). Published by Oxford University Press on behalf of the Royal Astronomical Society. All rights reserved.