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The impact of line-of-sight structures on measuring H0 with strong lensing time delays

Li, Nan; Becker, Christoph; Dye, Simon

The impact of line-of-sight structures on measuring H0 with strong lensing time delays Thumbnail


Authors

Nan Li

Christoph Becker

Simon Dye



Abstract

Measurements of the Hubble–Lemaitre constant from early- and local-Universe observations show a significant discrepancy. In an attempt to understand the origin of this mismatch, independent techniques to measure H0 are required. One such technique, strong lensing time delays, is set to become a leading contender amongst the myriad methods due to forthcoming large strong lens samples. It is therefore critical to understand the systematic effects inherent in this method. In this paper, we quantify the influence of additional structures along the line of sight by adopting realistic light-cones derived from the cosmoDC2 semi-analytical extragalactic catalogue. Using multiple-lens plane ray tracing to create a set of simulated strong lensing systems, we have investigated the impact of line-of-sight structures on time-delay measurements and in turn, on the inferred value of H0. We have also tested the reliability of existing procedures for correcting for line-of-sight effects. We find that if the integrated contribution of the line-of-sight structures is close to a uniform mass sheet, the bias in H0 can be adequately corrected by including a constant external convergence κext in the lens model. However, for realistic line-of-sight structures comprising many galaxies at different redshifts, this simple correction overestimates the bias by an amount that depends linearly on the median external convergence. We therefore conclude that lens modelling must incorporate multiple-lens planes to account for line-of-sight structures for accurate and precise inference of H0.

Citation

Li, N., Becker, C., & Dye, S. (2021). The impact of line-of-sight structures on measuring H0 with strong lensing time delays. Monthly Notices of the Royal Astronomical Society, 504(2), 2224-2234. https://doi.org/10.1093/mnras/stab984

Journal Article Type Article
Acceptance Date Apr 1, 2021
Online Publication Date Apr 13, 2021
Publication Date 2021-06
Deposit Date Nov 16, 2021
Publicly Available Date Mar 28, 2024
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 504
Issue 2
Pages 2224-2234
DOI https://doi.org/10.1093/mnras/stab984

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Publisher Licence URL
http://creativecommons.org/licenses/by/4.0/

Copyright Statement
© 2021 The Author(s).
Published by Oxford University Press on behalf of Royal Astronomical Society. This is an Open Access article distributed under the terms of the Creative
Commons Attribution License (http://creativecommons.org/licenses/by/4.0/), which permits unrestricted reuse, distribution, and reproduction in any medium,
provided the original work is properly cited.





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