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Where the Blue Stragglers Roam: Searching for a Link Between Formation and Environment

Published online by Cambridge University Press:  01 September 2007

Nathan Leigh ,
Alison Sills  and
Christian Knigge
Nathan Leigh
Affiliation:
Department of Physics and Astronomy, McMaster University, 1280 Main Street West, Hamilton, ON, L8S 4M1, Canada email: leighn@mcmaster.ca, asills@mcmaster.ca
Alison Sills
Affiliation:
Department of Physics and Astronomy, McMaster University, 1280 Main Street West, Hamilton, ON, L8S 4M1, Canada email: leighn@mcmaster.ca, asills@mcmaster.ca
Christian Knigge
Affiliation:
School of Physics and Astronomy, Southampton University, Highfield, Southampton, SO17 1BJ, UK email: christian@astro.soton.ac.uk
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Abstract

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Current observational evidence seems to indicate that blue stragglers are a dynamically created population, though exactly how the mechanism(s) of formation operates remains a mystery. We search for links between blue straggler formation and environment by considering only those stars found within one core radius of the cluster center. In so doing, we aim to isolate a sample that is representative of an approximately uniform cluster environment where, ideally, a single blue straggler formation mechanism is predominantly operating. Normalized blue straggler frequencies are found and apart from new anticorrelations with the central velocity dispersion and the half-mass relaxation time, we find no other statistically significant trends.

Concerns regarding the method of normalization used to calculate relative blue straggler frequencies are discussed, specifically whether the previously observed anticorrelation with total cluster mass (see Piotto et al. 2004) is a consequence of the normalization process. A new correlation between the observed number of blue stragglers in the core and the number predicted from single-single collisions alone is presented. This new link between formation and environment represents the first direct evidence that the blue straggler phenomenon has, at least in part, a collisional origin.

Keywords

blue stragglers – globular clusters: general
Type
Contributed Papers
Information
Proceedings of the International Astronomical Union , Volume 3 , Symposium S246: Dynamical Evolution of Dense Stellar Systems , September 2007 , pp. 331 - 335
Copyright
Copyright © International Astronomical Union 2008

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