Tracing the Dynamical History of the Globular Cluster 47 Tucanae

We use two stellar populations in the globular cluster 47 Tucanae to traceits dynamical history: blue stragglers and low mass main sequence stars. Weassumed that the blue stragglers were formed through stellar collisions in allregions of the cluster. We find that in the core of the cluster, models ofcollisional blue stragglers agree well with the observations as long as bluestragglers are still continuing to form and the mass function in the cluster isextremely biased towards massive stars (x=-8 where a Salpeter mass function hasx=+1.35). We show that such an extreme mass function is supported by directmeasurements of the luminosity function of main sequence stars in the centre ofthe cluster. In the middle region of our dataset (25'' to 130'' from thecluster centre), blue straggler formation seems to have stopped about half aGyr ago. In the outskirts of the cluster, our models are least successful atreproducing the blue straggler data. Taken at face value, they indicate thatblue straggler formation has been insignificant over the past billion years,and that a Salpeter mass function applies. However, it is more likely that thedominant formation mechanism in this part of the cluster is not the collisionalone, and that our models are not appropriate for this region of the cluster. Weconclude that blue stragglers can be used as tracers of dynamics in globularclusters, despite our incomplete understanding of how and where they wereformed.Comment: Accepted by Ap