Understanding the large inferred Einstein radii of observed low-mass galaxy clusters

Robertson, Andrew; Massey, Richard; Eke, Vincent

doi:10.1093/mnras/staa1076

Understanding the large inferred Einstein radii of observed low-mass galaxy clusters

Robertson, Andrew; Massey, Richard; Eke, Vincent

Authors

Dr Andrew Robertson andrew.robertson@durham.ac.uk
Academic Visitor

Professor Richard Massey r.j.massey@durham.ac.uk
Professor

Dr Vincent Eke v.r.eke@durham.ac.uk
Associate Professor

Abstract

We assess a claim that observed galaxy clusters with mass ∼1014M⊙ are more centrally concentrated than predicted in lambda cold dark matter (ΛCDM). We generate mock strong gravitational lensing observations, taking the lenses from a cosmological hydrodynamical simulation, and analyse them in the same way as the real Universe. The observed and simulated lensing arcs are consistent with one another, with three main effects responsible for the previously claimed inconsistency. First, galaxy clusters containing baryonic matter have higher central densities than their counterparts simulated with only dark matter. Secondly, a sample of clusters selected because of the presence of pronounced gravitational lensing arcs preferentially finds centrally concentrated clusters with large Einstein radii. Thirdly, lensed arcs are usually straighter than critical curves, and the chosen image analysis method (fitting circles through the arcs) overestimates the Einstein radii. After accounting for these three effects, ΛCDM predicts that galaxy clusters should produce giant lensing arcs that match those in the observed Universe.

Citation

Robertson, A., Massey, R., & Eke, V. (2020). Understanding the large inferred Einstein radii of observed low-mass galaxy clusters. Monthly Notices of the Royal Astronomical Society, 494(4), 4706-4712. https://doi.org/10.1093/mnras/staa1076

Journal Article Type	Article
Acceptance Date	Apr 16, 2020
Online Publication Date	Apr 24, 2020
Publication Date	2020-06
Deposit Date	Jun 24, 2020
Publicly Available Date	Jun 24, 2020
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	494
Issue	4
Pages	4706-4712
DOI	https://doi.org/10.1093/mnras/staa1076

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Copyright Statement
This article has been accepted for publication in Monthly notices of the Royal Astronomical Society. ©: 2020 The Author(s). Published by Oxford University Press on behalf of the Royal Astronomical Society. All rights reserved.