LY alpha Emission from Cooling Flows and Measures of the Dust Content of Rich Clusters of Galaxies

Abstract

We tabulate Ly α and UV continuum fluxes from measurements across the emission-line regions of 10 "cooling flow" clusters of galaxies. Comparison of Ly α emission fluxes obtained with the IUE satellite with optical Balmer emission fluxes is used to demonstrate that the lines of sight to the centers of these clusters show an average excess reddening E_B-V_ ~ 0.19 above foreground extinction. While some fraction of this may derive from localized extinction in the central (cooling flow) region of the cluster, a substantial portion of this effect should arise from an extended cluster component. We consider the case where this extinction originates in the hot intracluster gas of the cluster halo. Estimates for the corresponding 100 micron infrared emission, assuming grain properties similar to those of interstellar grains, place the expected emission at the ~1/2 Jy level for nearby clusters. Measurements from IRAS pointed mode observations of clusters are consistent with the expected values. These results are used to show that ISO and SIRTF may detect clusters to cosmological distances.