Probing the Dark Matter Radial Profile in Lens Galaxies and the Size of X-Ray Emitting Region in Quasars with Microlensing

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

The Astrophysical Journal, Volume 806, Issue 2, article id. 251, 7 pp. (2015).

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2015
Description
We use X-ray and optical microlensing measurements to study the shape of the dark matter density profile in the lens galaxies and the size of the (soft) X-ray emission region. We show that single epoch X-ray microlensing is sensitive to the source size. Our results, in good agreement with previous estimates, show that the size of the X-ray emission region scales roughly linearly with the black hole mass, with a half-light radius of {{R}}1/2≃ (24+/- 14){{r}}{\boldsymbol{g}} where {r}g={{GM}}{BH}/{c}2. This corresponds to a size of {log}({{R}}1/2/{cm})={15.6}-0.3+0.3 or ∼1 lt-day for a black hole mass of {M}{BH}={10}9 {M}ȯ . We simultaneously estimated the fraction of the local surface mass density in stars, finding that the stellar mass fraction is α = 0.20 ± 0.05 at an average radius of ∼ 1.9{R}e, where Re is the effective radius of the lens. This stellar mass fraction is insensitive to the X-ray source size and in excellent agreement with our earlier results based on optical data. By combining X-ray and optical microlensing data, we can divide this larger sample into two radial bins. We find that the surface mass density in the form of stars is α = 0.31 ± 0.15 and α = 0.13 ± 0.05 at (1.3+/- 0.3){R}e and (2.3+/- 0.3){R}e, respectively, in good agreement with expectations and some previous results.
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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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