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Scanning for dark matter subhaloes in Hubble Space Telescope imaging of 54 strong lenses

Nightingale, James W; He, Qiuhan; Cao, Xiaoyue; Amvrosiadis, Aristeidis; Etherington, Amy; Frenk, Carlos S; Hayes, Richard G; Robertson, Andrew; Cole, Shaun; Lange, Samuel; Li, Ran; Massey, Richard

Scanning for dark matter subhaloes in Hubble Space Telescope imaging of 54 strong lenses Thumbnail


James W Nightingale

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Dr Qiuhan He
Post Doctoral Research Associate

Xiaoyue Cao

Richard G Hayes

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Sam Lange
PGR Student Doctor of Philosophy

Ran Li


The cold dark matter (DM) model predicts that every galaxy contains thousands of DM subhaloes; almost all other DM models include a physical process that smooths away the subhaloes. The subhaloes are invisible, but could be detected via strong gravitational lensing, if they lie on the line of sight to a multiply imaged background source, and perturb its apparent shape. We present a predominantly automated strong lens analysis framework, and scan for DM subhaloes in Hubble Space Telescope imaging of 54 strong lenses. We identify five DM subhalo candidates, including two especially compelling candidates (one previously known in SLACS0946 + 1006) where a subhalo is favoured after all of our tests for systematics. We find that the detectability of subhaloes depends upon the assumed parametric form for the lens galaxy’s mass distribution, especially its degree of azimuthal freedom. Using separate components for DM and stellar mass reveals two DM subhalo candidates and removes four false positives compared to the single power-law mass model that is common in the literature. We identify 45 lenses without substructures, the number of which is key to statistical tests able to rule out models of, for example, warm or self-interacting DM. Our full analysis results are available at

Journal Article Type Article
Acceptance Date Nov 23, 2023
Online Publication Date Dec 4, 2023
Publication Date Jan 3, 2024
Deposit Date Feb 29, 2024
Publicly Available Date Feb 29, 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 527
Issue 4
Pages 10480-10506
Keywords Space and Planetary Science; Astronomy and Astrophysics
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