DARK MATTER MASS FRACTION IN LENS GALAXIES: NEW ESTIMATES FROM MICROLENSING

• Published in: The Astrophysical journal Vol. 799; no. 2; pp. 1 - 6
• Main Authors: Jimenez-Vicente, J, Villa, E Media, Kochanek, C S, Munoz, J A
• Format: Journal Article
• Language: English
• Published: United States 01.02.2015
• Subjects: ACCRETION DISKS; ASTROPHYSICS, COSMOLOGY AND ASTRONOMY; Dark matter; DENSITY; Estimates; GALAXIES; GRAVITATIONAL LENSES; Lenses; MASS; NONLUMINOUS MATTER; QUASARS; STARS; SURFACES; VISIBLE RADIATION
• ISSN: 1538-4357; 0004-637X; 1538-4357
• DOI: 10.1088/0004-637X/799/2/149

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 alpha = 0.21 + or - 0.14 near the Einstein radius of the lenses (~1-2 effective radii). The estimate for the average accretion disk size is (ProQuest: Formulae and/or non-USASCII text omitted) 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.