Open AccessThe internal structure of the lens PG1115+080: breaking degeneracies in the value of the Hubble constant
Author(s) -
Treu T.,
Koopmans L. V. E.
Publication year - 2002
Publication title -
monthly notices of the royal astronomical society
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 2.058
H-Index - 383
eISSN - 1365-2966
pISSN - 0035-8711
DOI - 10.1046/j.1365-8711.2002.06107.x
Subject(s) - physics , einstein radius , astrophysics , galaxy , hubble's law , mass ratio , radius , stellar mass , gravitational lens , fundamental plane (elliptical galaxies) , mass to light ratio , lens (geology) , mass fraction , star formation , redshift , lenticular galaxy , optics , computer security , computer science , thermodynamics , luminosity function
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 ρ∝ r −γ′ 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 ( 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 −1 Mpc −1 (68 per cent confidence level; Ω m = 0.3, Ω Λ = 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.