Journal Article

The edge-on spiral gravitational lens B1600 + 434

L. V. E. Koopmans, A. G. de Bruyn and N. Jackson

in Monthly Notices of the Royal Astronomical Society

Published on behalf of The Royal Astronomical Society

Volume 295, issue 3, pages 534-548
Published in print April 1998 | ISSN: 0035-8711
Published online April 1998 | e-ISSN: 1365-2966 | DOI: http://dx.doi.org/10.1046/j.1365-8711.1998.01226.x
The edge-on spiral gravitational lens B1600 + 434

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We present new observations of the gravitational lens (GL) system B1600 + 434, strongly suggesting that the lens is an edge-on spiral galaxy. These observations are used to constrain the mass model of the system, in particular the oblateness and velocity dispersion of the dark matter halo around the lensing galaxy. From an analytical model we find a lower limit on the halo oblateness qhalo = (c/a)ρ ≳ 0.4; more detailed numerical models give a lower limit of qhalo ≳ 0.5. We determine an average halo velocity dispersion of σhalo = 190 ± 15 km s−1 over all non-singular isothermal elliptical (NIE) halo models. Constraining the models to larger and more massive discs decreases this average by only 10 km s−1. A lower limit of σhalo ≳ 150 km s−1 is found, even for disc masses larger than the mass inside the Einstein radius. This lower limit indicates the need for a massive dark matter halo, contributing at least half of the mass inside the Einstein radius. Time-delay calculations give (54 ± 3)/h50 d for the NIE halo model and (70 ± 4)/h50 d for the modified Hubble profile (MHP) halo model. Although the time delay for both NIE and MHP halo models is well constrained on our parameter grid, it strongly depends on the halo surface density profile. We furthermore find that the presence of a flat luminous mass distribution can severely alter the statistical properties of the lens.

Keywords: galaxies: spiral; galaxies: structure; dark matter; distance scale; gravitational lensing

Journal Article.  0 words. 

Subjects: Astronomy and Astrophysics

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