The internal structure of the lens PG 1115 + 080 : breaking degeneracies in the value of the Hubble Constant
نویسنده
چکیده
We combine lensing, stellar kinematic and mass-to-light ratio constraints to build a twocomponent (luminous plus dark) mass model of the early-type lens galaxy in PG1115+080. We find a total mass density profile steeper than r, effectively ρ ∝ r ′ with γ = 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 (RE≈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: H0 = 59 +12 −7 ± 3 km s −1 Mpc (68% C.L.; Ωm = 0.3, ΩΛ=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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