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Self-interacting dark matter and small-scale gravitational lenses in galaxy clusters

Daneng Yang and Hai-Bo Yu
Phys. Rev. D 104, 103031 – Published 29 November 2021
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  • INTRODUCTION
  • MODELING THE CLUSTER SYSTEM
  • GRAVOTHERMAL COLLAPSE
  • STRONG-LENSING OBSERVABLES
  • DENSITY PROFILES
  • MOCK LENSED IMAGES
  • DISCUSSION AND CONCLUSIONS
  • ACKNOWLEDGMENTS
    • References

    Abstract

    Recently, Meneghetti et al. reported an excess of small-scale gravitational lenses in galaxy clusters. We study its implications for self-interacting dark matter (SIDM) compared with standard cold dark matter (CDM). We design controlled N-body simulations that incorporate observational constraints. The presence of early-type galaxies in cluster substructures can deepen gravitational potential and reduce tidal mass loss. Both scenarios require a relatively high baryon concentration in the substructure to accommodate the lensing measurements, and their tangential caustics are similar. The SIDM substructure can experience gravothermal collapse and produce a steeper density profile than its CDM counterpart, leading to a larger radial galaxy-galaxy strong-lensing cross section, although this effect is hard to observe. Our results indicate that SIDM can provide a unified explanation to small-scale lenses in galaxy clusters and stellar motion in dwarf galaxies.

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    • Received 15 March 2021
    • Revised 5 August 2021
    • Accepted 8 November 2021

    DOI:https://doi.org/10.1103/PhysRevD.104.103031

    © 2021 American Physical Society

    Physics Subject Headings (PhySH)

    1. Research Areas
    Dark matter
    Gravitation, Cosmology & AstrophysicsParticles & Fields

    Authors & Affiliations

    Daneng Yang1,2,* and Hai-Bo Yu2,†

    • 1Department of Physics, Tsinghua University, Beijing 100084, China
    • 2Department of Physics and Astronomy, University of California, Riverside, California 92521, USA

    • *yangdn@mail.tsinghua.edu.cn
    • †haiboyu@ucr.edu

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    Issue

    Vol. 104, Iss. 10 — 15 November 2021

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    Images

    • Figure 1
      Figure 1

      Left: Evolution of Vmax−Msub for the simulated SIDM (solid thick curves) and CDM (solid thin curves) benchmarks with different initial subhalo concentrations, denoted using deviations from the cosmological median at z=0: i.e., +3σ (magenta), +2σ (red), +1σ (green), and +0σ (blue). The arrows denote the direction of the evolution, and the final snapshot is at t=6  Gyr. CDM simulations without including the star component are also shown (dotted curves). For comparison, the average relation from strong-lensing observations (black dashed curve) [23], as well as the range (gray band) and the best-fit model relation (gray dashed curve) from their CDM simulations are displayed. Right: SIDM tangential (dashed curves) and radial (solid curves) GGSL cross sections vs source redshift, normalized to their corresponding CDM counterparts for t=6  Gyr. The color scheme is the same as the one in the left panel. The simulated CDM substructures without stars have a low surface density, and their lensing effect is negligible.

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    • Figure 2
      Figure 2

      Total (solid curves) and dark matter (dashed curves) density profiles for the SIDM (red) and CDM (gray) benchmarks with c200=12.4 (+2σ) at t=6  Gyr. The red and gray arrows denote their Einstein radii, respectively, assuming zs=3. The dark matter density profile from CDM simulations without stars is also shown (dotted curve); its lensing effect is negligible. Insert: Evolution of Vmax−rmax for the benchmarks with stars.

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    • Figure 3
      Figure 3

      Left: Tangential (dashed curves) and radial (solid curves) caustics for the simulated SIDM and CDM substructures with c200=12.4 (+2σ), together with four mock sources (circles). The corresponding critical lines and lensed images are shown in the middle and right panels, respectively, assuming zs=3. For the lens redshift zl=0.439 of MACSJ1206, 1 arcsec corresponds to 5.76 kpc.

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