Gravitational imaging through a triple source plane lens: revisiting the $Λ$CDM-defying dark subhalo in SDSSJ0946+1006
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arXiv
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| Format: | Preprint |
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2023
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| author | Ballard, Daniel J. Enzi, Wolfgang J. R. Collett, Thomas E. Turner, Hannah C. Smith, Russell J. |
| author_facet | Ballard, Daniel J. Enzi, Wolfgang J. R. Collett, Thomas E. Turner, Hannah C. Smith, Russell J. |
| contents | The $Λ$CDM paradigm successfully explains the large-scale structure of the Universe, but is less well constrained on sub-galactic scales. Gravitational lens modelling has been used to measure the imprints of dark substructures on lensed arcs, testing the small-scale predictions of $Λ$CDM. However, the methods required for these tests are subject to degeneracies among the lens mass model and the source light profile. We present a case study of the unique compound gravitational lens SDSSJ0946+1006, wherein a dark, massive substructure has been detected, whose reported high concentration would be unlikely in a $Λ$CDM universe. For the first time, we model the first two background sources in both I- and U-band HST imaging, as well as VLT-MUSE emission line data for the most distant source. We recover a lensing perturber at a $5.9σ$ confidence level with mass $\log_{10}(M_\mathrm{sub}/M_{\odot})=9.2^{+0.4}_{-0.1}$ and concentration $\log_{10}c=2.4^{+0.5}_{-0.3}$. The concentration is more consistent with CDM subhalos than previously reported, and the mass is compatible with that of a dwarf satellite galaxy whose flux is undetectable in the data at the location of the perturber. A wandering black hole with mass $\log_{10}(M_\mathrm{BH}/M_{\odot})=8.9^{+0.2}_{-0.1}$ is a viable alternative model. We systematically investigate alternative assumptions about the complexity of the mass distribution and source reconstruction; in all cases the subhalo is detected at around the $\geq5σ$ level. However, the detection significance can be altered substantially (up to $11.3σ$) by alternative choices for the source regularisation scheme. |
| format | Preprint |
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arxiv_https___arxiv_org_abs_2309_04535 |
| institution | arXiv |
| publishDate | 2023 |
| record_format | arxiv |
| spellingShingle | Gravitational imaging through a triple source plane lens: revisiting the $Λ$CDM-defying dark subhalo in SDSSJ0946+1006 Ballard, Daniel J. Enzi, Wolfgang J. R. Collett, Thomas E. Turner, Hannah C. Smith, Russell J. Cosmology and Nongalactic Astrophysics Astrophysics of Galaxies The $Λ$CDM paradigm successfully explains the large-scale structure of the Universe, but is less well constrained on sub-galactic scales. Gravitational lens modelling has been used to measure the imprints of dark substructures on lensed arcs, testing the small-scale predictions of $Λ$CDM. However, the methods required for these tests are subject to degeneracies among the lens mass model and the source light profile. We present a case study of the unique compound gravitational lens SDSSJ0946+1006, wherein a dark, massive substructure has been detected, whose reported high concentration would be unlikely in a $Λ$CDM universe. For the first time, we model the first two background sources in both I- and U-band HST imaging, as well as VLT-MUSE emission line data for the most distant source. We recover a lensing perturber at a $5.9σ$ confidence level with mass $\log_{10}(M_\mathrm{sub}/M_{\odot})=9.2^{+0.4}_{-0.1}$ and concentration $\log_{10}c=2.4^{+0.5}_{-0.3}$. The concentration is more consistent with CDM subhalos than previously reported, and the mass is compatible with that of a dwarf satellite galaxy whose flux is undetectable in the data at the location of the perturber. A wandering black hole with mass $\log_{10}(M_\mathrm{BH}/M_{\odot})=8.9^{+0.2}_{-0.1}$ is a viable alternative model. We systematically investigate alternative assumptions about the complexity of the mass distribution and source reconstruction; in all cases the subhalo is detected at around the $\geq5σ$ level. However, the detection significance can be altered substantially (up to $11.3σ$) by alternative choices for the source regularisation scheme. |
| title | Gravitational imaging through a triple source plane lens: revisiting the $Λ$CDM-defying dark subhalo in SDSSJ0946+1006 |
| topic | Cosmology and Nongalactic Astrophysics Astrophysics of Galaxies |
| url | https://arxiv.org/abs/2309.04535 |