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Session 73 - Gravitational Lensing.
Display session, Wednesday, January 15
Multiple strong lensing of a resolved source allows a unique high resolution reconstruction of the lensing mass. We present detailed mass models for CL0024, a rich cluster at z=0.39. A blue background galaxy (z=1.2-1.8) is imaged six times by the cluster. We model the cluster mass distribution as a superposition of resolved masses described by 121 parameters, and calculate chi-squared from a pixel-by-pixel comparison of the image to a model. We construct models based on elliptical mass distributions, rather than elliptical potentials that can lead to unphysical (negative) masses. This permits for the first time a separate measurement of mass associated with cluster galaxies and with the diffuse dark matter. The diffuse mass distribution inside 110 h^-1 kpc is consistent with an isothermal distribution with a smooth elliptical core. The half-density core size is 60h^-1 kpc, with an axial ratio of 1.6. We can rule out any significant mass substructure on scales larger than 15 h^-1 kpc in the central region. Mass traces light fairly well, out to at least 500 h^-1 kpc. We also present precise measurements of mass-to-light ratio vs radius, including diffuse intra-cluster light.
Program listing for Wednesday