Tracing the Dynamical History of the Globular Cluster 47 Tucanae

Abstract

We use two stellar populations in the globular cluster 47 Tucanae to trace its dynamical history: blue stragglers and low mass main sequence stars. We assumed that the blue stragglers were formed through stellar collisions in all regions of the cluster. We find that in the core of the cluster, models of collisional blue stragglers agree well with the observations as long as blue stragglers are still continuing to form and the mass function in the cluster is extremely biased towards massive stars (x=-8 where a Salpeter mass function has x=+1.35). We show that such an extreme mass function is supported by direct measurements of the luminosity function of main sequence stars in the centre of the cluster. In the middle region of our dataset (25'' to 130'' from the cluster centre), blue straggler formation seems to have stopped about half a Gyr ago. In the outskirts of the cluster, our models are least successful at reproducing the blue straggler data. Taken at face value, they indicate that blue straggler formation has been insignificant over the past billion years, and that a Salpeter mass function applies. However, it is more likely that the dominant formation mechanism in this part of the cluster is not the collisional one, and that our models are not appropriate for this region of the cluster. We conclude that blue stragglers can be used as tracers of dynamics in globular clusters, despite our incomplete understanding of how and where they were formed.

arXiv commentAccepted by ApJ

References in corpus (16)

• Distances and ages of NGC 6397, NGC 6752 and 47 Tuc
• HST color-magnitude diagrams of 74 galactic globular clusters in the HST F439W and F555W bands
• Relative Frequencies of Blue Stragglers in Galactic Globular Clusters: Constraints for the Formation Mechanisms
• The Frequency of Binary Stars in the Core of 47 Tucanae
• Blue straggler production in globular clusters
• Models for Old, Metal-Poor Stars with Enhanced alpha-Element Abundances. III. Isochrones and Isochrone Population Functions
• The contribution of primordial binaries to the blue straggler population in 47 Tucanae
• Discovery of another peculiar radial distribution of Blue Stragglers in Globular Clusters: The case of 47 Tuc
• Binary--single-star scattering VI. Automatic Determination of Interaction Cross Sections
• The blue stragglers formed via mass transfer in old open clusters
• The small Blue Straggler star population in the dense Galactic Globular Cluster NGC 6752
• The Distribution of Collisionally Induced Blue Stragglers in the Colour-Magnitude Diagram
• A Spectroscopic Analysis of Blue Stragglers, Horizontal Branch and Turn-Off Stars in Four Globular Clusters
• Resolving the Controversy Over the Core Radius of 47 Tucanae (NGC 104)
• The Formation Rate of Blue Stragglers in 47 Tucanae
• The Blue Straggler Population of the Globular Cluster M5: Comparison with M3

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• Where the Blue Stragglers Roam: Searching for a Link Between Formation and Environment
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• Blue straggler stars in dwarf spheroidal galaxies
• Blue straggler stars in dwarf spheroidal galaxies II: Sculptor and Fornax
• The ACS LCID project VII: the blue stragglers population in the isolated dSph galaxies Cetus and Tucana
• Gravitational waves from intermediate-mass black holes in young clusters
• Millisecond pulsars around intermediate-mass black holes in globular clusters
• HST/WFC3 Observations of Low-Mass Globular Clusters AM 4 and Palomar 13: Physical Properties and Implications for Mass Loss
• Formation and Evolution of Blue Stragglers in 47 Tucanae
• The Blue Straggler Population in Dwarf Galaxies
• Globular clusters of the Gaia Enceladus/Sausage -- I. Orbital and dynamical evolution on cosmological timescales