Observational constraints on the sub-galactic matter-power spectrum from galaxy-galaxy strong gravitational lensing

Bayer, Dorota; Chatterjee, S.; Koopmans, L. V. E.; Vegetti, Simona; McKean, J. P.; Treu, Tommaso; Fassnacht, Chris

doi:10.48550/arxiv.1803.05952

Cited by 28 publications

(41 citation statements)

References 55 publications

(94 reference statements)

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“…In particular, we observe a correlation between the logarithm of P log(κ) gt /P log(κ) lens (k) ∀ k and the logarithm of P s gt /P s lens (k) for k = O( k pc) with a correlation coefficient ρ ≈ 0.95 in our sample. Moreover, we find that the reconstructed sources show increased power at small scales with respect to the ground truth, which indicates a certain level of noise fitting, as also found by Bayer et al (2018). A log-normal source prior may mitigate this issue significantly as it restricts the source brightness values to positive values.…”

Section: Source and Time Delay Reconstructionsupporting

confidence: 72%

Systematic errors in strong gravitational lensing reconstructions, a numerical simulation perspective

Enzi,

Vegetti,

Despali

et al. 2019

Preprint

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We present the analysis of a sample of twenty-four galaxy-galaxy strong gravitational lens systems with a background source and deflectors from the Illustris-1 simulation. We create mock lensing observations with a data quality comparable to known samples such as the SLACS lenses, to study the degeneracy between the complex mass distribution of the lenses, subhaloes, the surface brightness distribution of the sources, and the time delays. Using a novel inference framework based on Approximate Bayesian Computation, we find that for all the considered lens systems, an elliptical and cored power-law mass density distribution provides a good fit to the data. However, due to the presence of unphysical cores in the simulated lenses, most reconstructions are affected by some form of the Source Position Transformation. The latter leads to a systematic underestimation of the source sizes by 50 per cent on average, and an underestimation of the time delays by up to 53 per cent. On the other hand, we find no degeneracy between complexity in the lensing potential and the inferred amount of substructure. We recover an average total projected mass fraction in subhaloes of f sub < 1.7 − 2.0 × 10 −3 at the 68 per cent confidence level which is consistent with zero and in agreement with the fact that all subhaloes had been removed from the simulation. Our work highlights the need for even higher-resolution simulations to quantify the lensing effect of more realistic galactic potentials better. Finally, our results confirm that additional observational constraints may be required to break existing degeneracies.

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Section: Source and Time Delay Reconstructionsupporting

confidence: 72%

Systematic errors in strong gravitational lensing reconstructions, a numerical simulation perspective

Enzi,

Vegetti,

Despali

et al. 2019

Preprint

Self Cite

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“…Ref. [85] placed an upper bound on the convergence power spectrum due to subhalos using lens system SDSS J0252+0039 (z l = 0.280, z s = 0.982) 11 . Their upper bound on the power spectrum was significantly higher than the expected amplitude due to subhalos in a CDM scenario, but interestingly, according to our results, for this redshift combination we expect the line-of-sight contribution to dominate.…”

Section: Discussionmentioning

confidence: 99%

Quantifying the Line-of-Sight Halo Contribution to the Dark Matter Convergence Power Spectrum from Strong Gravitational Lenses

Şengül,

Tsang,

Rivero

et al. 2020

Preprint

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Galaxy-galaxy strong gravitational lenses have become a popular probe of dark matter (DM) by providing a window into structure formation on the smallest scales. In particular, the convergence power spectrum of subhalos within lensing galaxies has been suggested as a promising observable to study DM. However, the distances involved in strong-lensing systems are vast, and we expect the relevant volume to contain line-of-sight (LOS) halos that are not associated with the main lens. We develop a formalism to calculate the effect of LOS halos as an effective convergence power spectrum. The multi-lens plane equation couples the angular deflections of consecutive lens planes, but by assuming that the perturbations due to the LOS halos are small, we show that they can be projected onto the main-lens plane as effective subhalos. We test our formalism by simulating lensing systems using the full multi-plane lens equation and find excellent agreement. We show how the relative contribution of LOS halos and subhalos depends on the source and lens redshift, as well as the assumed halo and subhalo mass functions. For a fiducial system with fraction of DM halo mass in substructure f sub = 0.4% for subhalo masses [10 5 − 10 8 ]M , the interloper contribution to the power spectrum is at least several times greater than that of subhalos for source redshifts zs 0.5. Furthermore, it is likely that for the SLACS and BELLS lenses the interloper contribution dominates: f sub 2% (4%) is needed for subhalos to dominate in SLACS (BELLS), which is higher than current upper bounds on f sub for our mass range. Since the halo mass function is better understood from first principles, the dominance of interlopers in galaxy-galaxy lenses with high-quality imaging can be seen as a significant advantage when translating this observable into a constraint on DM.

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“…Finding a proper summary statistic is a challenging part of ABC and it is beyond the scope of this work to investigate the many possible candidate summary statistics. Instead, following Bayer et al (2018), we use the power spectrum of the best-fit image residuals to construct a summary statistic that we hope can extract information on the number of low-mass dark matter haloes perturbing the lens.…”

Section: Abc Inference Through Forward Modellingmentioning

confidence: 99%

“…Most studies have focused on determining a theoretical relation between the power spectrum of the convergence field and that of the image residuals after fitting a smooth 'macro model' to the lens galaxy mass distribution Díaz Rivero et al 2018;Cyr-Racine et al 2019). There is one example using real data, in which Bayer et al (2018) analysed image residuals of the system SDSS J0252+0039, obtaining a detection of power much higher than the prediction of the cold dark matter (CDM) model. There remain a number of questions as to what assumptions are appropriate for this technique.…”

Section: Introductionmentioning

confidence: 99%

A forward-modelling method to infer the dark matter particle mass from strong gravitational lenses

He,

Robertson,

Nightingale

et al. 2020

Preprint

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A fundamental prediction of the cold dark matter (CDM) model of structure formation is the existence of a vast population of dark matter haloes extending to subsolar masses. By contrast, other possibilities for the nature of the dark matter, such as a warm thermal relic or a sterile neutrino (WDM) predict a cutoff in the mass function at a mass of ∼ 10 8 M . We use mock observations to demonstrate the viability of a forward modelling approach to extract information on the cosmological number density of low-mass dark matter haloes along the line-of-sight to galaxy-galaxy strong lenses. This can be used to constrain the mass of a thermal relic dark matter particle, 𝑚 DM . With 50 strong lenses at Hubble Space Telescope resolution and signal-to-noise (similar to the existing SLACS survey), the expected 2𝜎 constraint for CDM is 𝑚 DM > 3.7 keV. If, however, the dark matter is a warm particle of 𝑚 DM = 2.2 keV, one could rule out 𝑚 DM > 3.2 keV. Our [Approximate Bayesian Computation] method can be extended to the large samples of strong lenses that will be observed by future space telescopes, potentially to rule out the standard CDM model of cosmogony. To aid future survey design, we quantify how these constraints will depend on data quality (spatial resolution and integration time) as well as on the lensing geometry (source and lens redshifts).

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Observational constraints on the sub-galactic matter-power spectrum from galaxy-galaxy strong gravitational lensing

Cited by 28 publications

References 55 publications

Systematic errors in strong gravitational lensing reconstructions, a numerical simulation perspective

Systematic errors in strong gravitational lensing reconstructions, a numerical simulation perspective

Quantifying the Line-of-Sight Halo Contribution to the Dark Matter Convergence Power Spectrum from Strong Gravitational Lenses

A forward-modelling method to infer the dark matter particle mass from strong gravitational lenses

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