Other
Scientific paper
Dec 2001
adsabs.harvard.edu/cgi-bin/nph-data_query?bibcode=2001aas...19916005b&link_type=abstract
American Astronomical Society, 199th AAS Meeting, #160.05; Bulletin of the American Astronomical Society, Vol. 34, p.570
Other
Scientific paper
Our knowledge of the dark matter halos of elliptical galaxies is still limited, in contrast to the case for spiral galaxies. Here we report on an investigation of the dark matter halo of a z=0.484 elliptical galaxy, which is the lens in the optical Einstein ring system 0047-2808. Studying an Einstein ring has the advantage of the large number of constraints these resolved structures provide in modeling the mass distribution. Through spectroscopy, we can study the velocity dispersion profiles in the ring lens and directly compare the inferences from stellar dynamics and lens models. We obtained major-axis rotational velocity and velocity dispersion kinematics by spatially-resolved Keck/LRIS long-slit data at a relatively high resolution of R≈ 3000. By combining this kinematic data on the radial dependence of the line-of-sight velocity dispersion with an HST/WFPC2 F555W image of the lens and source we construct a detailed self-consistent model of the mass radial profile and the stellar dynamics in the lensing galaxy. The Einstein ring of radius rE=1.18 arcsec is formed by a z=3.596 star-forming galaxy, and the mass enclosed within rE is ME=2.9*E11h100-1 Msun. We use this as the the normalization of parametrized mass models, and calculate the best-fitting spherically-symmetric dynamical models. We measure the central stellar velocity dispersion to be σ c=(240+/- 10) km/s, in broad agreement with that inferred from the lensing (σ DM=(253+/- 10) km/s. Using the Jeans equation with velocity anisotropy, we have computed a range of dynamical models, and conclude that in both mass-traces-light and singular-isothermal cases some anisotropy is required, β ≈0.2-0.3. The isothermal (dark matter) case is marginally preferred. Future measurements extending far beyond 1 Re (e.g. with X-rays) will be more sensitive to the influence of dark matter.
Bunker Andrew J.
Davis Martin
Moustakas Leonidas A.
Warren Stephen J.
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