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Testing strong lensing subhalo detection with a cosmological simulation

He, Qiuhan; Nightingale, James; Robertson, Andrew; Amvrosiadis, Aristeidis; Cole, Shaun; Frenk, Carlos S; Massey, Richard; Li, Ran; Amorisco, Nicola C; Metcalf, R Benton; Cao, Xiaoyue; Etherington, Amy

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Dr Qiuhan He
Post Doctoral Research Associate

Andrew Robertson

Ran Li

Nicola C Amorisco

R Benton Metcalf

Xiaoyue Cao


Strong gravitational lensing offers a compelling test of the cold dark matter paradigm, as it allows for subhaloes with masses of ∼109 M⊙ and below to be detected. We test commonly-used techniques for detecting subhaloes superposed in images of strongly lensed galaxies. For the lens we take a simulated galaxy in a ∼1013 M⊙ halo grown in a high-resolution cosmological hydrodynamical simulation, which we view from two different directions. Though the resolution is high, we note the simulated galaxy still has an artificial core which adds additional complexity to the baryon dominated region. To remove particle noise, we represent the projected galaxy mass distribution by a series of Gaussian profiles which precisely capture the features of the projected galaxy. We first model the lens mass as a (broken) power-law density profile and then search for small haloes. Of the two projections, one has a regular elliptical shape, while the other has distinct deviations from an elliptical shape. For the former, the broken power-law model gives no false positives and correctly recovers the mass of the superposed small halo, but for the latter we find false positives and the inferred halo mass is overestimated by ∼4 − 5 times. We then use a more complex model in which the lens mass is decomposed into stellar and dark matter components. In this case, we show that we can capture the simulated galaxy’s complex projected structures and correctly infer the input small halo.


He, Q., Nightingale, J., Robertson, A., Amvrosiadis, A., Cole, S., Frenk, C. S., …Etherington, A. (2023). Testing strong lensing subhalo detection with a cosmological simulation. Monthly Notices of the Royal Astronomical Society, 518(1), 220-239.

Journal Article Type Article
Publication Date 2023-01
Deposit Date Oct 11, 2022
Publicly Available Date Oct 11, 2022
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 518
Issue 1
Pages 220-239


Accepted Journal Article (1.9 Mb)

Copyright Statement
This article has been accepted for publication in Monthly notices of the Royal Astronomical Society. ©: 2022 The Author(s). Published by Oxford University Press on behalf of the Royal Astronomical Society. All rights reserved.

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