A Salpeter IMF and an NFW halo: Disentangling the dark and stellar mass through precise lens modelling of a double-source-plane system reinforces the canonical model of elliptical galaxies
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| Natura: | Preprint |
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2026
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| author | Li, Tian Collett, Thomas E. Krawczyk, Coleman M. Granata, Giovanni Enzi, Wolfgang J. R. Ballard, Daniel J. Lines, Natalie E. P. de Murieta, Ana Sainz Weisenbach, Luke Ryczanowski, Dan |
| author_facet | Li, Tian Collett, Thomas E. Krawczyk, Coleman M. Granata, Giovanni Enzi, Wolfgang J. R. Ballard, Daniel J. Lines, Natalie E. P. de Murieta, Ana Sainz Weisenbach, Luke Ryczanowski, Dan |
| contents | We present a strong lensing analysis of the double source plane lens J0946+1006 (colloquially "Jackpot" lens) to measure the inner dark matter density profile, the stellar-to-halo mass ratio, and the stellar initial mass function normalisation using a two component stellar plus dark matter mass model. The stellar mass follows a multi-Gaussian expansion light model with a free global mass-to-light ratio and an allowed radial $M/L$ gradient, while the dark matter is described by an elliptical generalised NFW halo. The double-source-plane geometry provides additional leverage against the mass-sheet transformation and helps constrain the radial mass profile. Despite allowing both a radial stellar $M/L$ gradient and a generalised NFW halo, the data prefer the canonical picture: an approximately constant stellar mass-to-light ratio with a Salpeter-like IMF normalisation, and a dark matter halo consistent with NFW. We infer $M_{\star} = 4.4^{+0.25}_{-0.39}\times 10^{11}\,M_{\odot}$ and an inner halo slope $γ_{\rm in}^{\rm halo} = 1.04^{+0.10}_{-0.14}$. The halo mass is $M_{200}^{\rm halo} = 1.11^{+0.37}_{-0.32}\times 10^{13}\,M_{\odot}$, implying $\log_{10}(M_{200}/M_{\star})=1.41^{+0.13}_{-0.14}$. At fixed halo mass, the inferred stellar mass lies $\sim0.1$ dex above typical literature stellar halo mass relations at similar redshift, which is comparable to the intrinsic scatter of these relations. We expect this approach to provide a practical template for future dark matter studies with the large double-source-plane lens samples from Euclid. |
| format | Preprint |
| id |
arxiv_https___arxiv_org_abs_2602_20889 |
| institution | arXiv |
| publishDate | 2026 |
| record_format | arxiv |
| spellingShingle | A Salpeter IMF and an NFW halo: Disentangling the dark and stellar mass through precise lens modelling of a double-source-plane system reinforces the canonical model of elliptical galaxies Li, Tian Collett, Thomas E. Krawczyk, Coleman M. Granata, Giovanni Enzi, Wolfgang J. R. Ballard, Daniel J. Lines, Natalie E. P. de Murieta, Ana Sainz Weisenbach, Luke Ryczanowski, Dan Astrophysics of Galaxies Cosmology and Nongalactic Astrophysics We present a strong lensing analysis of the double source plane lens J0946+1006 (colloquially "Jackpot" lens) to measure the inner dark matter density profile, the stellar-to-halo mass ratio, and the stellar initial mass function normalisation using a two component stellar plus dark matter mass model. The stellar mass follows a multi-Gaussian expansion light model with a free global mass-to-light ratio and an allowed radial $M/L$ gradient, while the dark matter is described by an elliptical generalised NFW halo. The double-source-plane geometry provides additional leverage against the mass-sheet transformation and helps constrain the radial mass profile. Despite allowing both a radial stellar $M/L$ gradient and a generalised NFW halo, the data prefer the canonical picture: an approximately constant stellar mass-to-light ratio with a Salpeter-like IMF normalisation, and a dark matter halo consistent with NFW. We infer $M_{\star} = 4.4^{+0.25}_{-0.39}\times 10^{11}\,M_{\odot}$ and an inner halo slope $γ_{\rm in}^{\rm halo} = 1.04^{+0.10}_{-0.14}$. The halo mass is $M_{200}^{\rm halo} = 1.11^{+0.37}_{-0.32}\times 10^{13}\,M_{\odot}$, implying $\log_{10}(M_{200}/M_{\star})=1.41^{+0.13}_{-0.14}$. At fixed halo mass, the inferred stellar mass lies $\sim0.1$ dex above typical literature stellar halo mass relations at similar redshift, which is comparable to the intrinsic scatter of these relations. We expect this approach to provide a practical template for future dark matter studies with the large double-source-plane lens samples from Euclid. |
| title | A Salpeter IMF and an NFW halo: Disentangling the dark and stellar mass through precise lens modelling of a double-source-plane system reinforces the canonical model of elliptical galaxies |
| topic | Astrophysics of Galaxies Cosmology and Nongalactic Astrophysics |
| url | https://arxiv.org/abs/2602.20889 |