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

Abstract

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 $f_{\mathrm{sub}}=0.4\%$ for subhalo masses $[10^5-10^8]{\mathrm{M}}_{\odot }$, the interloper contribution to the power spectrum is at least several times greater than that of subhalos for source redshifts $z_s\gtrsim 0.5$. Furthermore, it is likely that for the SLACS and BELLS lenses the interloper contribution dominates: $f_{\mathrm{sub}}\gtrsim 2\%$ ($4\%$) is needed for subhalos to dominate in SLACS (BELLS), which is higher than current upper bounds on $f_{\mathrm{sub}}$ 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.

24 pages, 8 figures, Matches accepted version, v3: Fixed a typo in Eq. C4 in the appendix. No changes in the derivations

References in corpus (12)

• Beasts of the Southern Wild: Discovery of nine Ultra Faint satellites in the vicinity of the Magellanic Clouds
• The halo mass function from the dark ages through the present day
• The stellar mass-halo mass relation of isolated field dwarfs: a critical test of $\Lambda$CDM at the edge of galaxy formation
• Inference of the Cold Dark Matter substructure mass function at z=0.2 using strong gravitational lenses
• Dark matter subhalos and the dwarf satellites of the Milky Way
• Analytic models of plausible gravitational lens potentials
• Shaken and Stirred: The Milky Way's Dark Substructures
• Mining for Dark Matter Substructure: Inferring subhalo population properties from strong lenses with machine learning
• Rhapsody. II. Subhalo Properties and the Impact of Tidal Stripping From a Statistical Sample of Cluster-Size Halos
• On the Power Spectrum of Dark Matter Substructure in Strong Gravitational Lenses
• On the density profile of dark matter substructure in gravitational lens galaxies
• Direct Detection of Dark Matter Substructure in Strong Lens Images with Convolutional Neural Networks

Cited by in corpus (24)

• lenstronomy II: A gravitational lensing software ecosystem
• Gravitational wave lensing as a probe of halo properties and dark matter
• Line-of-sight effects in strong gravitational lensing
• Substructure Detection Reanalyzed: Dark Perturber shown to be a Line-of-Sight Halo
• TDCOSMO III: Dark matter substructure meets dark energy -- the effects of (sub)halos on strong-lensing measurements of $H_0$
• From Images to Dark Matter: End-To-End Inference of Substructure From Hundreds of Strong Gravitational Lenses
• GIGA-Lens: Fast Bayesian Inference for Strong Gravitational Lens Modeling
• Inferring the concentration of dark matter subhalos perturbing strongly lensed images
• Extracting the Subhalo Mass Function from Strong Lens Images with Image Segmentation
• Image segmentation for analyzing galaxy-galaxy strong lensing systems
• Astrophysical Tests of Dark Matter Self-Interactions
• One never walks alone: the effect of the perturber population on subhalo measurements in strong gravitational lenses
• Decoding Dark Matter Substructure without Supervision
• Gravitational lenses in arbitrary space-times
• Inferring subhalo effective density slopes from strong lensing observations with neural likelihood-ratio estimation
• Interlopers speak out: studying the dark universe using small-scale lensing anisotropies
• Anisotropic strong lensing as a probe of dark matter self-interactions
• Weak lensing of strong lensing: beyond the tidal regime
• DESI-253.2534+26.8843: A New Einstein Cross Spectroscopically Confirmed with VLT/MUSE and Modeled with GIGA-Lens
• A forward-modelling method to infer the dark matter particle mass from strong gravitational lenses
• Galaxy-galaxy strong lens perturbations: line-of-sight haloes versus lens subhaloes
• Probing Dark Matter with Strong Gravitational Lensing through an Effective Density Slope
• ALMA Measurement of 10 kpc-scale Lensing Power Spectra towards the Lensed Quasar MG J0414+0534
• Across the Universe: GW231123 as a magnified and diffracted black hole merger