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Article Dans Une Revue Monthly Notices of the Royal Astronomical Society Année : 2010

Detection of a dark substructure through gravitational imaging

S. Vegetti
  • Fonction : Auteur
L. V. E. Koopmans
  • Fonction : Auteur
A. Bolton
  • Fonction : Auteur
T. Treu
  • Fonction : Auteur

Résumé

We report the detection of a dark substructure - undetected in the Hubble Space Telescope HST ACS F814W image - in the gravitational lens galaxy SDSSJ0946+1006 (the `double Einstein ring'), through direct gravitational imaging. The detection of a small mass concentration in the surface density maps, at 4.3 kpc from the galaxy centre, has a strong statistical significance. We confirm this detection by modelling the substructure with a tidally truncated pseudo-Jaffe density profile; in that case the substructure mass is Msub = (3.51 +/- 0.15) × 109Msolar, precisely where also the surface density map shows a strong convergence peak (Bayes factor ; equivalent to a ~16σ detection). The result is robust under substantial changes in the model. We set a lower limit of (M/L)V,solar >~ 120Msolar/LV,solar (3σ) inside a sphere of 0.3 kpc centred on the substructure (rtidal = 1.1kpc). The mass and luminosity limit of this substructure are consistent with Local Group results if the substructure had a virial mass of ~1010Msolar before accretion and formed at z >~ 10. Our detection implies a projected dark matter mass fraction in substructure at the radius of the inner Einstein ring of f = 2.15+2.05-1.25 per cent [68 per cent confidence level (CL)] in the mass range 4 × 106- 4 × 109Msolar, assuming α = 1.9 +/- 0.1 (with dN/dm ~ m). Assuming a flat prior on α, between 1.0 and 3.0, increases this to f = 2.56+3.26-1.50 per cent (68 per cent CL). The likelihood ratio is ~0.5 between these fractions and that from simulations (fN-body ~ 0.003). Hence the inferred dark matter mass fraction in substructure, admittedly based on a single-lens system, is large but still consistent with predictions.
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Dates et versions

hal-03646011 , version 1 (04-09-2022)

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S. Vegetti, L. V. E. Koopmans, A. Bolton, T. Treu, R. Gavazzi. Detection of a dark substructure through gravitational imaging. Monthly Notices of the Royal Astronomical Society, 2010, 408, pp.1969-1981. ⟨10.1111/j.1365-2966.2010.16865.x⟩. ⟨hal-03646011⟩
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