Gravitational imaging through a triple source plane lens: revisiting the $Λ$CDM-defying dark subhalo in SDSSJ0946+1006

• DOI: 10.48550/arxiv.2309.04535
• Publication Date: 2023-01-01
• Authors: Daniel Ballard; Wolfgang Enzi; Thomas S Collett; Hannah C. Turner; Russell J. Smith
• Keywords: Strong gravitational lensing; Mass distribution

The $\Lambda$CDM paradigm successfully explains the large-scale structure of Universe, but is less well constrained on sub-galactic scales. Gravitational lens modelling has been used to measure imprints dark substructures lensed arcs, testing small-scale predictions $\Lambda$CDM. However, methods required for these tests are subject degeneracies among mass model and source light profile. We present a case study unique compound gravitational SDSSJ0946+1006, wherein dark, massive substructure detected, whose reported high concentration would be unlikely in universe. For first time, we two background sources both I- U-band HST imaging, as VLT-MUSE emission line data most distant source. recover lensing perturber at $5.9\sigma$ confidence level with $\log_{10}(M_\mathrm{sub}/M_{\odot})=9.2^{+0.4}_{-0.1}$ $\log_{10}c=2.4^{+0.5}_{-0.3}$. more consistent CDM subhalos than previously reported, compatible that dwarf satellite galaxy flux undetectable location perturber. A wandering black hole $\log_{10}(M_\mathrm{BH}/M_{\odot})=8.9^{+0.2}_{-0.1}$ viable alternative model. systematically investigate assumptions about complexity distribution reconstruction; all cases subhalo detected around $\geq5\sigma$ level. detection significance can altered substantially (up $11.3\sigma$) by choices regularisation scheme.