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Lens Galaxies vs. CDM

Charles R. Keeton
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Abstract

By directly probing mass distributions, gravitational lensing offers several new tests of the CDM paradigm. Lens statistics place upper limits on the dark matter content of elliptical galaxies. Galaxies built from CDM mass distributions are too concentrated to satisfy these limits, so lensing extends the ``concentration problem'' in CDM to elliptical galaxies. The central densities of the model galaxies are too low on ~10 pc scales to agree with the lack of central images in observed lenses. The flux ratios of four-image lenses imply a substantial population of dark matter clumps with a typical mass ~10^6 Msun. Thus, lensing implies the need for a mechanism that reduces dark matter densities on kiloparsec scales without erasing structure on smaller scales.

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Charles R. Keeton. 2001-12-14. Lens Galaxies vs. CDM. https://arxiv.org/abs/astro-ph/0112350

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