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Researchers analyzed the dark matter distribution in a subhalo within the gravitational lensing system JVAS B1938+666 and found that alternative dark matter models—specifically self-interacting dark matter (SIDM) and fuzzy dark matter—fit the observed density profile significantly better than the standard cold dark matter model. The reconstruction reveals a dense core approximately 0.5 kiloparsecs in radius with a central density of about 25 million solar masses per cubic kiloparsec, consistent with observations of dwarf galaxies in our Local Group. The SIDM model was statistically favored over fuzzy dark matter with strong evidence (Bayes factor of 14.44).
Why it matters
This finding provides observational support for alternative dark matter theories that could resolve long-standing discrepancies between cold dark matter predictions and observations at small scales, particularly the "core-cusp problem" where observed galaxies show smoother central density distributions than simulations predict. The consistency with Local Group dwarf galaxies suggests these alternative models may better explain dark matter behavior across different scales.
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⚠️ Preprint – Noch nicht peer-reviewed
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Abstract: The nature of dark matter remains unknown, motivating the study of fuzzy/wave dark matter (FDM/$psi$DM) and self-interacting dark matter (SIDM) as alternative frameworks to address small-scale discrepancies in halo profiles inferred from observations. This study presents a non-parametric reconstruction of the mass distribution of the previously-found, dark subhalo in the strong-lensing system JVAS B1938+666. Compared with the standard Navarro-Frenk-White (NFW) profile, both SIDM and $psi$DM ($m_{psi}=1.32^{+0.22}_{-0.31}times 10^{-22} , rm eV$) provide significantly better fits to the resulting density profile. Moreover, the SIDM model is favored over $psi$DM with a Bayes factor of 14.44. The reconstructed density profile features a characteristic kiloparsec-scale core ($r_c approx 0.5 , rm kpc$) with central density $rho_c approx 2.5times 10^{7}, rm M_{odot} , kpc^{-3} $, exhibiting remarkable consistency with the core-halo mass scaling relations observed in Local Group dwarf spheroidals. These findings offer insights that may help address the core-cusp discrepancy in $Lambda$CDM substructure predictions.
Source: A dense dark matter core of the subhalo in the strong lensing system JVAS B1938+666