Refining the dynamical clock for star clusters

Journal
Date Issued
2016
Author(s)
Lanzoni, B.
•
Ferraro, F. R.
•
Alessandrini, E.
•
•
Vesperini, E.
•
Raso, S.
DOI
Abstract
We used a sample of 25 Galactic globular clusters to empirically measure the parameter A + recently introduced by Alessandrini et al., and defined as the area enclosed between the cumulative radial distribution of blue straggler stars (BSSs) and that of a reference population. Based on N-body simulations, this parameter is expected to efficiently measure the level of BSS central segregation. Observationally, for a proper cluster-to-cluster comparison we use {A}{rh}+, I.e., the value of the parameter determined out to the half-mass radius in each system. We find that {A}{rh}+ nicely correlates with the position of the minimum of the BSS normalized radial distribution and with the cluster central relaxation time. This demonstrates that it is a sensitive indicator of the cluster dynamical age as traced by the spatial segregation of the BSS population. In the context of the “stellar system dynamical clock,” this parameter provides a new clock-hand, which is easier to determine observationally and allows a more robust measure of the cluster dynamical age.
Volume
833
Issue
2
Start page
L29
Uri
Url
Issn Identifier
2041-8205
Ads BibCode
2016ApJ...833L..29L
Rights
open.access
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