Publication Date:
2015-12-20
Description:
We measure the projected density profile, shape and alignment of the stellar and dark matter mass distribution in 11 strong-lens galaxies. We find that the projected dark matter density profile – under the assumption of a Chabrier stellar initial mass function – shows significant variation from galaxy to galaxy. Those with an outermost image beyond ~10 kpc are very well fit by a projected Navarro–Frenk–White (NFW) profile; those with images within 10 kpc appear to be more concentrated than NFW, as expected if their dark haloes contract due to baryonic cooling. We find that over several half-light radii, the dark matter haloes of these lenses are rounder than their stellar mass distributions. While the haloes are never more elliptical than e dm = 0.2, their stars can extend to e * 〉 0.2. Galaxies with high dark matter ellipticity and weak external shear show strong alignment between light and dark; those with strong shear ( 0.1) can be highly misaligned. This is reassuring since isolated misaligned galaxies are expected to be unstable. Our results provide a new constraint on galaxy formation models. For a given cosmology, these must explain the origin of both very round dark matter haloes and misaligned strong-lens systems.
Print ISSN:
0035-8711
Electronic ISSN:
1365-2966
Topics:
Physics
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