The Dark Matter, Gas and Galaxy Distributions in Abell 2218: A Weak Gravitational Lensing and X-ray Analysis

G. Squires; N. Kaiser; A. Babul; G. Fahlman; D. Woods; D. M. Neumann; H. Böhringer

doi:10.1086/177085

paper

The Dark Matter, Gas and Galaxy Distributions in Abell 2218: A Weak Gravitational Lensing and X-ray Analysis

arXiv:astro-ph/9507008 · doi:10.1086/177085

Abstract

We report on the detection of dark matter in the cluster Abell 2218 using the weak gravitational distortion of background galaxies. We find a highly significant, coherent detection of the distortion in the images of the background galaxies. The inferred 2D mass distribution has a peak that is coincident with the optical and X-ray centroid. The qualitative distributions of the cluster light, the X-ray emission and the dark matter are similar and the projected total mass, gas, and light surface densities are consistent with a $r^{- 1}$ profile at distance of $r > 18 0^{''}$ from the cluster cD galaxy. Using the weak lensing technique, we determine a lower bound for the total mass in A2218 of $(3.9 \pm 0.7) \times 1 0^{14}$ ~h $^{- 1}$ ~M $_{⊙}$ within a fiducial aperture of radius 0.4~h $^{- 1}$ Mpc. The associated cluster mass-to-light ratio is $(440 \pm 80)$ ~h~ $M_{⊙} / L_{⊙ B}$ . The mass estimated by the weak lensing method is consistent with that inferred from the X-ray data under the assumption of hydrostatic equilibrium and we derive an upper bound for the gas-to-total mass ratio at 400~h $^{- 1}$ kpc of $M_{g a s} / M_{t o t} = (0.04 \pm 0.02)$ h $^{- 3/2}$ .

25 pages, Latex, no figures. Complete version with figures available by anon ftp at ftp://ftp.cita.utoronto.ca/ftp/cita/squires/a2218

The Dark Matter, Gas and Galaxy Distributions in Abell 2218: A Weak Gravitational Lensing and X-ray Analysis

Abstract

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