Journal Article

Lensing and dynamics in two simple steps

A. Agnello, M. W. Auger and N. W. Evans

in Monthly Notices of the Royal Astronomical Society: Letters

Published on behalf of The Royal Astronomical Society

Volume 429, issue 1, pages L35-L39
Published in print February 2013 |
Published online November 2012 | e-ISSN: 1745-3933 | DOI: http://dx.doi.org/10.1093/mnrasl/sls020

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We present a ready-to-use method to constrain the density distribution in spherically symmetric early-type galaxy lenses. Assuming a power-law density profile, then joint use of the virial theorem and the lens equation yields simple formulae for the power-law index (or logarithmic density gradient). Any dependence on orbital anisotropy can be tightly constrained or even erased completely. Our results rely just on surface brightnesses and line-of-sight kinematics, making deprojection unnecessary. We revisit three systems that have already been examined in the literature (the Cosmic Horseshoe, the Jackpot and B1608+656) and provide our estimates. Finally, we show that the method yields a good approximation for the density profile even when the true profile is a broken power law, albeit with a mild bias towards isothermality.

Keywords: gravitational lensing: strong; galaxies: elliptical and lenticular, cD; galaxies: kinematics and dynamics; dark matter

Journal Article.  3760 words.  Illustrated.

Subjects: Astronomy and Astrophysics

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