FAR-INFRARED EMISSION FROM ABELL CLUSTERS

We have examined the frequency with which central dominant galaxies are sources of far-infrared emission in a complete sample of clusters of galaxies. Previous searches for far-infrared emission (FIR; IRAS 60 and 100 mu m measurements) from dominant cluster galaxies (Bregman, McNamara, & O'Connell 1990; Grabelsky & Ulmer 1990) using small, inhomogeneous samples have found 20%-50% of clusters to have significant FIR emission. In a new study, we analyzed the 60 and 100 mu m emission properties of cD galaxies in a complete sample of 163 Abell Clusters. For comparison, a control sample of 207 blank fields was analyzed to determine the distribution of spurious detections, which is greater than expected from Gaussian statistics. The contribution of Galactic cirrus at 60 and 100 mu m to non-Gaussian noise is clearly demonstrated by the correspondence of a 98% confidence level to a signal to noise of 4 or 4.5 rather than to a signal-to-noise ratio of 2 as expected from Gaussian statistics. After correcting for contaminated fields and spurious detections, we find that similar to 10% of cD galaxies in rich clusters are sources of FIR emission. This rate is lower than that quoted in previous studies, which we attribute to our correction for spurious sources, and to the differences in sample selection and average redshift between our study and previous work. Typical detected cDs have FIR luminosities of similar to 3 x 10(44) ergs s(-1), which is comparable to the blue luminosities from these objects and an order of magnitude greater than the X-ray luminosities produced n the cores of clusters. Dust masses derived from the 60 and 100 mu m fluxes are similar to 10(7) M.. Because only similar to 10% of the clusters have high FIR luminosities, such strong emission is probably a transient state for an individual cluster.