Constraints on Cool Gas in Rich Clusters of Galaxies

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Cool gas should be present in galaxy clusters due to stripping of galactic gas, infall onto the cluster, and from cooling flows. We searched for this gas through resonance absorption line observations from low-ionization metal line gas toward six background quasars. Both cooling flow and non-cooling flow clusters were observed, with lines of sight from the inner to outer parts of the cluster (0.2 <= rₚroj/Rcluster <= 0.7). The HST/FOS spectra failed to detect Fe II or Mg II absorption at the cluster redshift, with 1-sigma upper limits on the ion column densities of N <= 10¹2 - 10¹3 cm-2. The failure to detect absorption lines implies that the cool cluster gas either is more highly ionized or it has a low covering factor.