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The internal structure of the lens PG1115+080: breaking degeneracies in the value of the Hubble Constant

Tommaso Treu·Leon V. E. Koopmans
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Abstract

We combine lensing, stellar kinematic and mass-to-light ratio constraints to build a two-component (luminous plus dark) mass model of the early-type lens galaxy in PG1115+080. We find a total mass density profile steeper than r^-2, effectively rho r^-gamma' with gamma'=2.35+-0.1+-0.05 (random + systematic). The stellar mass fraction is f*=0.67(+0.20/-0.25)+-0.03 inside the Einstein Radius (R_E 1.2 effective radii). The dynamical mass model breaks the degeneracies in the mass profile of the lens galaxy and allows us to obtain a value of the Hubble Constant that is no longer dominated by systematic errors: H_0=59(+12/-7)+-3 km/s/Mpc (68 percent C.L.; Omega_m=0.3, Omega_L=0.7). The offset of PG1115+080 from the Fundamental Plane might indicate deviations from homology of the mass profile of some early-type galaxies.

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Tommaso Treu, Leon V. E. Koopmans. 2002-09-30. The internal structure of the lens PG1115+080: breaking degeneracies in the value of the Hubble Constant. https://doi.org/10.1046/j.1365-8711.2002.06107.x

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