Detection of ionized gas in the globular cluster 47 Tucanae

We report the detection of ionized intracluster gas in the globular cluster 47 Tucanae. Pulsars in this cluster with a negative period derivative, whi ch must lie in the distant half of the cluster, have significantly higher m easured integrated electron column densities than the pulsars with a positi ve period derivative. We derive the plasma density within the central few p arsecs of the cluster using two different methods that yield consistent val ues. Our best estimate of n(e) = 0.067 +/- 0.015 cm(-3) is about 100 times the free electron density of the interstellar medium in the vicinity of 47 Tucanae, and the ionized gas is probably the dominant component of the intr acluster medium.