Evidence for substructure in lens galaxies?

Peter Schneider (MPA); Shude Mao

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Evidence for substructure in lens galaxies?

Shude Mao, Peter Schneider (MPA)

Astrophysics · Submitted 16 Jul 1997

abstract compiled · 2026-09-23 · no language-model review

The authors' main claim We argue that at least in one case (B 1422+231) these difficulties are not due to a `wrong' parametrization of the lens model, but that the discrepancy between observed and model-predicted flux ratios are due to substructure in the lens.

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What the abstract itself states, as probabilities: claims first 0.03 · states limitation 0.27 · human participants 0.01 · controlled comparison 0.10 · randomized assignment 0.01 · states quantitative result 0.07 · compares with prior results 0.52 · mentions code or data availability 0.02.

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We discuss whether one should expect that multiply imaged QSOs can be understood with `simple' lens models which contain a handful of parameters. Whereas for many lens systems such simple mass models yield a remarkably good description of the observed properties, there are some systems which are notoriously difficult to understand quantitatively. We argue that at least in one case (B 1422+231) these difficulties are not due to a `wrong' parametrization of the lens model, but that the discrepancy between observed and model-predicted flux ratios are due to substructure in the lens. Similar to microlensing for optical fluxes, such substructure can distort also the radio flux ratios predicted by `simple' mass models, in particular for highly magnified images, without appreciably changing image positions. Substructure also does not change the time delay significantly and therefore has little effect on the determination of the Hubble constant using time delays. We quantify these statements with several simple scenarios for substructure, and propose a strategy to model lens systems in which substructure is suspected.

background contribution method result interpretation main claim

What the classifier reports for each sentence. The number is the probability it gave the label.
#	sentence	role	the authors' own work	states the main conclusion	strength
s0	We discuss whether one should expect that multiply imaged QSOs can be understood with `simple' lens models which contain a handful of parameters.	background 0.92	0.24	0.03	unclear 0.76
s1	Whereas for many lens systems such simple mass models yield a remarkably good description of the observed properties, there are some systems which are notoriously difficult to understand quantitatively.	background 0.95	0.10	0.03	asserted 0.99
s2	We argue that at least in one case (B 1422+231) these difficulties are not due to a `wrong' parametrization of the lens model, but that the discrepancy between observed and model-predicted flux ratios are due to substructure in the lens.	result 0.50	0.62	0.86	asserted 0.59
s3	Similar to microlensing for optical fluxes, such substructure can distort also the radio flux ratios predicted by `simple' mass models, in particular for highly magnified images, without appreciably changing image positions.	interpretation 0.59	0.20	0.09	hedged possibility 0.59
s4	Substructure also does not change the time delay significantly and therefore has little effect on the determination of the Hubble constant using time delays.	result 0.59	0.48	0.08	asserted 0.97
s5	We quantify these statements with several simple scenarios for substructure, and propose a strategy to model lens systems in which substructure is suspected.	contribution 0.88	0.85	0.11	asserted 0.93

What kind of paper the classifier reports this is: position or commentary 0.85 · evidence from argument 0.77.

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arXiv listing abstract v1

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The paper

Original abstract

We discuss whether one should expect that multiply imaged QSOs can be understood with `simple' lens models which contain a handful of parameters. Whereas for many lens systems such simple mass models yield a remarkably good description of the observed properties, there are some systems which are notoriously difficult to understand quantitatively. We argue that at least in one case (B 1422+231) these difficulties are not due to a `wrong' parametrization of the lens model, but that the discrepancy between observed and model-predicted flux ratios are due to substructure in the lens. Similar to microlensing for optical fluxes, such substructure can distort also the radio flux ratios predicted by `simple' mass models, in particular for highly magnified images, without appreciably changing image positions. Substructure also does not change the time delay significantly and therefore has little effect on the determination of the Hubble constant using time delays. We quantify these statements with several simple scenarios for substructure, and propose a strategy to model lens systems in which substructure is suspected.

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References

Forward citations

Cited by 13 Pith papers

Reviewed papers in the Pith corpus that reference this work. Sorted by Pith novelty score. Full citation record

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Factorized attention (separating spatial and temporal interactions) gives lower classification loss than joint attention or a ConvLSTM baseline for causal, on-the-fly classification of asynchronous multi-band image streams.
Wave-optics imprints of dark matter subhalos on strongly lensed gravitational waves. II. Saddle images and detectability
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Subhalos produce percent-level modulations in saddle and minimum images; matched-filter analysis yields >5σ combined detections in 62% of realizations for fiducial sources near caustics, projecting 10-20 substructure ...
JWST lensed quasar dark matter survey IV: Stringent warm dark matter constraints from the joint reconstruction of extended lensed arcs and quasar flux ratios
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Adding extended lensed arcs to quasar flux ratios in 28 JWST lenses tightens the dark-matter free-streaming limit to m_hm < 10^7.4 M⊙ (galacticus prior) and gives the most precise lensing measurement of subhalo abundance.

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Core-collapsed self-interacting dark matter halos in the Concerto simulations reach high enough central densities to match the perturbing masses inferred in J0946, B1938, SDP.81, and SPT2147-50.
Detecting Lensing-Induced Diffraction in Astrophysical Gravitational Waves
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A boson of mass near 10^-22 eV reproduces large-scale cosmology while naturally producing cored halos, suppressing low-mass sub-halos, and slowing dynamical friction enough to keep Fornax's globular clusters in orbit.
Addressing position anomalies in the Strong Gravitational Lensing System HS~0810+2554 through Dark Matter Subhalos
astro-ph.CO 2026-08 conditional novelty 5.0 of 10

A simulated CDM subhalo population reduces the position-fit chi2 of HS 0810+2554 from 60.4 to 1.6, showing the anomaly can be explained within standard cold dark matter.
Probing Dark Matter Substructure with Image Number Anomaly in Strong Lensing Systems
astro-ph.CO 2025-11 unverdicted novelty 5.0 of 10

Null detection of extra lensed images in 3500 mock systems constrains PBH abundance to ≲0.04-0.125% and excludes FDM masses below 0.4-3.5×10^{-22} eV at 95% CL depending on angular resolution.
Strong gravitational lensing of explosive transients
astro-ph.CO 2019-07 accept novelty 3.0 of 10

Strong lensing of explosive transients, with their fast light curves and compact sizes, enables precise time-delay cosmography, small-scale dark matter probes, and wave-optics tests that lensed quasars cannot deliver.
A New Era in the Quest for Dark Matter
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astro-ph.CO 2026-10 accept

Strong gravitational lensing provides a purely gravitational probe that measures H0 at 3% precision from 11 lensed quasars and hints at dark matter self-interaction from dense subhalos.

How later papers used it

139 later papers cite it

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1 later paper by other authors is listed below: 1 cited it as support.

Cites it as support 1 paper

Said that the boosted amplitude and phase fluctuations can be explained by the nonlinear dependence of convergence perturbations on magnification factors, as in this paper.

Amplitude and phase fluctuations of gravitational waves magnified by strong gravitational lensing (2022) · 0.95 · paraphrased: the licence does not allow quoting

How the literature uses it

44 arXiv papers cite this in 58 sentences

Each citing sentence is taken from the citing paper's LaTeX source and typed by Pith's classifier. A label appears at probability 0.8 or more (0.95 for support), a contest at 0.7 or more; the quoted words are the citing authors'. How each label was checked · JSON

Papers whose main result relates to this one's

Found among the papers closest to this one by title and main claim. Pith's classifier compared each pair's main results and a second model family confirmed the relation; checked against two further families, shown conflicts agreed 118 times in 120 and shown same results 218 times in 239. The quoted sentence is the other paper's main claim.

States the same result 1 paper

The difficulties in fitting these lens systems turn out to be similar to the case of some real gravitationally lensed systems, thus possibly providing evidence for the presence and strong influence of substructure in the primary lens galaxy.

B1422+231: The influence of mass substructure on strong lensing · 0.80

Papers citing it · 47 sentences without a confident label

Cites it as background 11 papers

While this method was proposed at the turn of the century [ref] , until recently most analyses of strong gravitational lenses in this context have been done under the assumption that the additional clumps lie within the dark matter halo of the main lens.

Quantifying the Line-of-Sight Halo Contribution to the Dark Matter Convergence Power Spectrum from Strong Gravitational Lenses · Introduction · 0.97
It has long been known that the macro-substructure degeneracy is a significant confounding factor for determining the true origin of flux anomalies in strongly lensed quasar data [ref] .

Mapping the Information Geometry of an Unresolved Dark Matter Population using a Differentiable Strong Lensing Simulator · On the macro-substructure degeneracy · 0.86
Previous studies have also demonstrated that strong gravitational lensing is highly sensitive to DM substructure and can provide stringent tests of small-scale structure [ref] .

Addressing position anomalies in the Strong Gravitational Lensing System HS~0810+2554 through Dark Matter Subhalos · Discussion · 0.81

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