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14 May 2021
Article (Scientific journals)
Galaxy-lens determination of H0: the effect of the ellipse + shear modelling assumption
Gomer, Matthew  ; Williams, Liliya L. R.
2021 • In Monthly Notices of the Royal Astronomical Society, 504 (1), p. 1340-1354
Peer reviewed


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This article has been accepted for publication in MNRAS ©: 2020. Published by Oxford University Press on behalf of the Royal Astronomical Society. All rights reserved.

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Keywords :
gravitational lensing: strong; galaxies: haloes; structure; cosmology: distance scale; Astrophysics - Astrophysics of Galaxies; Astrophysics - Cosmology and Nongalactic Astrophysics
Abstract :
[en] Galaxy lenses are frequently modelled as an elliptical mass distribution with external shear and isothermal spheres to account for secondary and line-of-sight galaxies. There is statistical evidence that some fraction of observed quads are inconsistent with these assumptions, and require a dipole-like contribution to the mass with respect to the light. Simplifying assumptions about the shape of mass distributions can lead to the incorrect recovery of parameters such as H[SUB]0[/SUB]. We create several tests of synthetic quad populations with different deviations from an elliptical shape, then fit them with an ellipse + shear model, and measure the recovered values of H[SUB]0[/SUB]. Kinematic constraints are not included. We perform two types of fittings - one with a single point source and one with an array of sources emulating an extended source. We carry out two model-free comparisons between our mock quads and the observed population. One result of these comparisons is a statistical inconsistency not yet mentioned in the literature: the image distance ratios with respect to the lens centre of observed quads appear to span a much wider range than those of synthetic or simulated quads. Bearing this discrepancy in mind, our mock populations can result in biases on H[SUB]0[/SUB] $\sim 10{{\ \rm per\ cent}}$ .
Disciplines :
Space science, astronomy & astrophysics
Author, co-author :
Gomer, Matthew ;  Université de Liège - ULiège > Département d'astrophys., géophysique et océanographie (AGO) > Origines Cosmologiques et Astrophysiques (OrCa)
Williams, Liliya L. R.;  School of Physics and Astronomy, University of Minnesota, 116 Church Street SE, Minneapolis, MN 55455, USA)
Language :
Title :
Galaxy-lens determination of H0: the effect of the ellipse + shear modelling assumption
Publication date :
01 June 2021
Journal title :
Monthly Notices of the Royal Astronomical Society
Publisher :
Oxford University Press, Oxford, United Kingdom
Volume :
Issue :
Pages :
Peer reviewed :
Peer reviewed
European Projects :
H2020 - 787886 - COSMICLENS - Cosmology with Strong Gravitational Lensing
Funders :
CE - Commission Européenne


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