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Session 86 - Measurement of Cosmological Parameters.
Oral session, Wednesday, January 17
1st Floor, La Villita Assembly Building
The thermal and kinematic components of the S-Z effect have distinct spectral shapes and can be separated by measurements at two or more mm wavelengths. We have made measurements of the Sunyaev-Zel'dovich (S-Z) effect at mm wavelengths with the specific goals of determining the value of the Hubble Constant, H_0, and the peculiar velocities of galaxy clusters, v_pec. In a band centered at 2.1mm, we have detected a decrement in the brightness of the Cosmic Microwave Background (CMB) in the direction of A2163 (z=.20) with a significance of greater than 10 \sigma. By comparing the morphology of the S-Z and low energy X-ray surface brightnesses we have constrained models for the thermal structure of the intracluster (IC) gas. We determine, in general agreement with recent ASCA results, that the IC gas temperature decreases beyond 3 core radii. When uncertainties due to peculiar velocity, astrophysical confusion, IC gas temperature, clumping and asphericity of the IC gas are taken into account, we determine H_0(q_0=\frac12) = 72.6^+47_-33\,kms^-1Mpc^-1. In a band centered at 1.1mm, we have made the first significant detection of a brightness increment due the S-Z thermal effect. We have observed this cluster in a third band centered at 1.4mm; combining all the data we are able to limit the peculiar velocity to v_pec = -400^+810_-990\,kms^-1. Measurements of the cluster A1689 (z=.18) in the 2.1mm and 1.4mm bands have been used to limit its peculiar velocity to v_pec = -360^+510_-690\,kms^-1.
Program listing for Wednesday