The Internal Structure and Formation of Early-Type Galaxies: The Gravitational Lens System MG 2016+112 at z = 1.004

Treu, T. & Koopmans, L. V. E., 1-Aug-2002, In : The Astrophysical Journal. 575, 1, p. 87-94

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We combine our recent measurements of the velocity dispersion and the surface brightness profile of the lens galaxy D in the system MG 2016+112 (z=1.004) with constraints from gravitational lensing to study its internal mass distribution. We find the following: (1) dark matter accounts for more than 50% of the total mass within the Einstein radius (99% confidence limit [CL]), whereas ~75% is the more likely contribution. In particular, we can exclude at the 8 σ level that mass follows light inside the Einstein radius with a constant mass-to-light ratio (M/L). (2) The total mass distribution inside the Einstein radius is well described by a density profile ~r-γ', with an effective slope γ'=2.0+/-0.1+/-0.1, including random and systematic uncertainties. (3) The offset of galaxy D from the local fundamental plane independently constrains the stellar M/L and matches the range derived from our models, leading to a more stringent lower limit of more than 60% on the fraction of dark matter within the Einstein radius (99% CL). Under the assumption of adiabatic contraction, we show that the inner slope of the dark matter halo before the baryons collapsed to form the lens galaxy is γi
Original languageEnglish
Pages (from-to)87-94
JournalThe Astrophysical Journal
Issue number1
Publication statusPublished - 1-Aug-2002


  • Cosmology: Dark Matter, Galaxies: Elliptical and Lenticular, cD, Galaxies: Formation, Galaxies: Kinematics and Dynamics, Galaxies: Structure, Cosmology: Gravitational Lensing

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