Dark Matter Mass Fraction in Lens Galaxies: New Estimates from Microlensing

Jiménez-Vicente, J.; Mediavilla, E.; Kochanek, C. S.; Muñoz, J. A.
Bibliographical reference

The Astrophysical Journal, Volume 799, Issue 2, article id. 149, 6 pp. (2015).

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We present a joint estimate of the stellar/dark matter mass fraction in lens galaxies and the average size of the accretion disk of lensed quasars based on microlensing measurements of 27 quasar image pairs seen through 19 lens galaxies. The Bayesian estimate for the fraction of the surface mass density in the form of stars is α = 0.21 ± 0.14 near the Einstein radius of the lenses (~1-2 effective radii). The estimate for the average accretion disk size is R1/2=7.9+3.8-2.6\sqrt{M/0.3 M_ȯ } light days. The fraction of mass in stars at these radii is significantly larger than previous estimates from microlensing studies assuming quasars were point-like. The corresponding local dark matter fraction of 79% is in good agreement with other estimates based on strong lensing or kinematics. The size of the accretion disk inferred in the present study is slightly larger than previous estimates.
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Relativistic and Theoretical Astrophysics

Introduction Gravitational lenses are a powerful tool for Astrophysics and Cosmology. The goals of this project are: i) to obtain a robust determination of the Hubble constant from the time delay measured between the images of a lensed quasar; ii) to study the individual and statistical properties of dark matter condensations in lens galaxies from

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