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arXiv · 1209.2554

Lensing and Dynamics in Two Simple Steps

A. Agnello·M. W. Auger·N. W. Evans
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Abstract

We present a ready-to-use method to constrain the density distribution in 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.

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A. Agnello, M. W. Auger, N. W. Evans. 2012-09-12. Lensing and Dynamics in Two Simple Steps. https://doi.org/10.1093/mnrasl%2Fsls020

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