Galaxy–galaxy strong lens perturbations: line-of-sight haloes versus lens subhaloes

He, Qiuhan; Li, Ran; Frenk, Carlos S.; Nightingale, J. W.; Cole, Shaun; Amorisco, Nicola C.; Massey, Richard; Robertson, Andrew; Etherington, Amy; Amvrosiadis, Aristeidis; Cao, Xiaoyue

doi:10.1093/mnras/stac759

Cited by 14 publications

(4 citation statements)

References 65 publications

(51 reference statements)

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“…Our islands may be smaller than theirs in part because of our threshold of x HI > 0.5 for a cell to be part of an island, which ignores many partially ionized cells, especially in the models with faint sources. Still, the spread between our models is similar to the range found in[80] and larger than that in[81], giving us confidence that our range of scenarios is representative 14. When we fit the stacked absorption spectra following[82], we allow the normalization of the flux to float in the fit, as is done in[40].…”

supporting

confidence: 58%

“…The Lyman-α forest flux power spectrum is sensitive to P lin (k) up to wavenumber k ≈ 50 h Mpc −1 , with the most recent measurements placing tight limits on the parameter space of CDM alternatives [5][6][7][8][9][10][11]. 1 Probing P lin (k) on smaller scales, flux ratio measurements in strong gravitational lenses are currently sensitive to perturbations by halos with masses M 2 × 10 7 h −1 M , corresponding to k ≈ 160 h Mpc −1 [12][13][14]. Future observations by the James Webb Space Telescope (JWST) aim to extend this sensitivity to M ∼ 2 × 10 6 h −1 M , or k ≈ 340 h Mpc −1 (JWST GO-02046; PI Nierenberg).…”

Section: Introductionmentioning

confidence: 99%

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Small-scale clumping of dark matter and the mean free path of ionizing photons at z = 6

Cain

D’Aloisio

Iršič

et al. 2023

J. Cosmol. Astropart. Phys.

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Recently, the mean free path of ionizing photons in the z = 6 intergalactic medium (IGM) was measured to be very short, presenting a challenge to existing reionization models. At face value, the measurement can be interpreted as evidence that the IGM clumps on scales M ≲ 108 M ⊙, a key but largely untested prediction of the cold dark matter (CDM) paradigm. Motivated by this possibility, we study the role that the underlying dark matter cosmology plays in setting the z > 5 mean free path. We use two classes of models to contrast against the standard CDM prediction: (1) thermal relic warm dark matter (WDM), representing models with suppressed small-scale power; (2) an ultralight axion exhibiting a white noise-like power enhancement. Differences in the mean free path between the WDM and CDM models are subdued by pressure smoothing and the possible contribution of neutral islands to the IGM opacity. For example, comparing late reionization scenarios with a fixed volume-weighted mean neutral fraction of 20% at z = 6, the mean free path is 19 (45)% longer in a WDM model with mx = 3 (1) keV. The enhanced power in the axion-like model produces better agreement with the short mean free path measured at z = 6. However, drawing robust conclusions about cosmology is hampered by large uncertainties in the reionization process, extragalactic ionizing background, and thermal history of the Universe. This work highlights some key open questions about the IGM opacity during reionization.

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supporting

confidence: 58%

Section: Introductionmentioning

confidence: 99%

Small-scale clumping of dark matter and the mean free path of ionizing photons at z = 6

Cain

D’Aloisio

Iršič

et al. 2023

J. Cosmol. Astropart. Phys.

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“…This means that the mass contribution of the LOS halos is very small as compared to that of the deflector, at least for this configuration. Other works attempt to determine the effects of LOS halos; see, for example, Hogg et al (2022), He et al (2022).…”

Section: Resultsmentioning

confidence: 99%

Statistical inference for strong gravitational lensing observations in the presence of dark matter

Negrete‐Serrato

Ureña–López

2023

Astron Nachr

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We study the properties of strong lenses generated by dark matter galaxy halos in the Universe and the statistical inference process to understand the density profile of the lens. For that, we used mock data of strong gravitational lenses using the publicly available software paltas, which is a pipeline based on the well-known package lenstronomy and written in Python. The deflectors are modeled according to the so-called elliptical power law lens profile, and the background cosmology is assumed to be that of the standard cosmological model ΛCDM. The generated lensing observations include the contribution of dark matter substructure in the form of either subhalos or halos along the line of sight. In both cases, the underlying profile is the Navarro-Frenk-White one, which corresponds to the cold dark matter model. Performing a statistical inference process on these mock observations, our final objective is to identify the influence of the substructure on the inferred parameters that describe the lens profile.

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“…would be a smoking gun of the 'clumpy' Cold Dark Matter (CDM) model, they would also perturb the multiple images (Natarajan & Springel 2004;Vegetti et al 2010;Vegetti et al 2014;Li et al 2016Li et al , 2017Hezaveh et al 2016;Ritondale et al 2019;Despali et al 2019;He et al 2021;Amorisco et al 2022;Nightingale et al 2022).…”

mentioning

confidence: 99%

Strong gravitational lensing's `external shear' is not shear

Etherington¹,

Nightingale²,

Massey³

et al. 2023

Preprint

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The distribution of mass in galaxy-scale strong gravitational lenses is often modelled as an elliptical power law plus 'external shear', which notionally accounts for neighbouring galaxies and cosmic shear. We show that it does not. Except in a handful of rare systems, the best-fit values of external shear do not correlate with independent measurements of shear: from weak lensing in 45 Hubble Space Telescope images, or in 50 mock images of lenses with complex distributions of mass. Instead, the best-fit shear is aligned with the major or minor axis of 88% of lens galaxies; and the amplitude of the external shear increases if that galaxy is disky. We conclude that 'external shear' attached to a power law model is not physically meaningful, but a fudge to compensate for lack of model complexity. Since it biases other model parameters that are interpreted as physically meaningful in several science analyses (e.g. measuring galaxy evolution, dark matter physics or cosmological parameters), we recommend that future studies of galaxy-scale strong lensing should employ more flexible mass models.

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Galaxy–galaxy strong lens perturbations: line-of-sight haloes versus lens subhaloes

Cited by 14 publications

References 65 publications

Small-scale clumping of dark matter and the mean free path of ionizing photons at z = 6

Small-scale clumping of dark matter and the mean free path of ionizing photons at z = 6

Statistical inference for strong gravitational lensing observations in the presence of dark matter

Strong gravitational lensing's `external shear' is not shear

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