Effects of galaxy-halo alignment and adiabatic contraction on gravitational lens statistics

• Published in: Monthly notices of the Royal Astronomical Society Vol. 391; no. 2; pp. 653 - 662
• Main Authors: Minor, Quinn E., Kaplinghat, Manoj
• Format: Journal Article
• Language: English
• Published: Oxford, UK Blackwell Publishing Ltd 01.12.2008; Blackwell Science; Oxford University Press
• Subjects: Astronomy; Astrophysics; Dark matter; Earth, ocean, space; Exact sciences and technology; Galaxy: structure; gravitational lensing; Stars & galaxies; Statistics; Galaxy: structure; gravitational lensing; dark matter; Galaxy halo; Gravitational lenses; Gravitational contraction; Gravitational lensing; Probability; Alignment; Dark matter; Galaxy structure; Cold dark matter; Correlations; Multiplicity; Saturn satellite; Models; Early type galaxies; Pan; Ellipsoid; Sky surveys
• DOI: 10.1111/j.1365-2966.2008.13777.x
• ISSN: 0035-8711

We study the strong gravitational lens statistics of triaxial cold dark matter haloes occupied by central early-type galaxies. We calculate the image separation distribution for double, cusp and quad configurations. The ratios of image multiplicities at large separations are consistent with the triaxial NFW model, and at small separations are consistent with the singular isothermal ellipsoid model. At all the separations, the total lensing probability is enhanced by adiabatic contraction. If no adiabatic contraction is assumed, naked cusp configurations become dominant at ≈2.5 arcsec, which is inconsistent with the data. We also show that at small-to-moderate separations (≲5 arcsec) the image multiplicities depend sensitively on the alignment of the shapes of the luminous and dark matter projected density profiles. In contrast to other properties that affect these ratios, the degree of alignment does not have a significant effect on the total lensing probability. These correlations may therefore be constrained by comparing the theoretical image separation distribution to a sufficiently large lens sample from future wide and deep sky surveys such as Pan-Stars, LSST and JDEM. Understanding the correlations in the shapes of galaxies and their dark matter halo is important for future weak lensing surveys.