Limits on the Peculiar Velocities of Two Distant Clusters Using the Kinematic Sunyaev‐Zeldovich Effect

Abstract

We report millimeter-wavelength observations of the Sunyaev-Zeldovich (S-Z) e ect in two distant galaxy clusters. A relativistically correct analysis of the S-Z data is combined with the results of X-ray observations to determine the radial peculiar velocities of the clusters. We observed Abell 2163 (v r ) (z \ 0.201) in three millimeter-wavelength bands centered at 2.1, 1.4, and 1.1 mm. We report a signicant detection of the thermal component of the S-Z e ect seen as both a decrement in the brightness of the CMB at 2.1 mm and as an increment at 1.1 mm. Including uncertainties due to the calibration of the instrument, distribution and temperature of the intracluster gas, and astrophysical confusion, a simultaneous t to the data in all three bands gives km s~1 at 68% condence. We v r \ ]490 ~880 `1370 observed Abell 1689 (z \ 0.181) in the 2.1 and 1.4 mm bands. Including the same detailed accounting of uncertainty, a simultaneous t to the data in both bands gives km s~1. The v r \ ]170 ~630 `815 limits on the peculiar velocities of A2163 and A1689 correspond to deviations from the uniform Hubble ow of [2%3%.