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Relative Frequencies of Blue Stragglers in Galactic Globular Clusters: Constraints for the Formation Mechanisms

Piotto, Giampaolo and de Angeli, Francesca and King, Ivan R. and Djorgovski, S. G. and Bono, Giuseppe and Cassisi, Santi and Meylan, Georges and Recio-Blanco, Alejandra and Rich, R. M. and Davies, Melvyn B. (2004) Relative Frequencies of Blue Stragglers in Galactic Globular Clusters: Constraints for the Formation Mechanisms. Astrophysical Journal, 604 (2). L109-L112. ISSN 0004-637X. doi:10.1086/383617.

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We discuss the main properties of the Galactic globular cluster (GC) blue straggler stars (BSSs), as inferred from our new catalog containing nearly 3000 BSSs. The catalog has been extracted from the photometrically homogeneous V versus (B-V) color-magnitude diagrams (CMDs) of 56 GCs, based on Wide Field Planetary Camera 2 images of their central cores. In our analysis, we used consistent relative distances based on the same photometry and calibration. The number of BSSs has been normalized to obtain relative frequencies (F_(BSS)) and specific densities (N_S) using different stellar populations extracted from the CMD. The cluster F_(BSS) is significantly smaller than the relative frequency of field BSSs. We find a significant anticorrelation between the BSS relative frequency in a cluster and its total absolute luminosity (mass). There is no statistically significant trend between the BSS frequency and the expected collision rate. The value of F_(BSS) does not depend on other cluster parameters, apart from a mild dependence on the central density. Post-core-collapse clusters act like normal clusters as far as the BSS frequency is concerned. We also show that the BSS luminosity function for the most luminous clusters is significantly different, with a brighter peak and extending to brighter luminosities than in the less luminous clusters. These results imply that the efficiency of BSS production mechanisms and their relative importance vary with the cluster mass.

Item Type:Article
Related URLs:
URLURL TypeDescription Paper
Djorgovski, S. G.0000-0002-0603-3087
Rich, R. M.0000-0003-0427-8387
Additional Information:© 2004 The American Astronomical Society. Received 2004 January 16; accepted 2004 February 16; published 2004 March 4 Based on observations with the NASA/ESA Hubble Space Telescope, obtained at the Space Telescope Science Institute, which is operated by the Association of Universities for Research in Astronomy, Inc., under NASA contract NAS 5-26555. This research was supported by the Ministero dell’Istruzione, Università e Ricerca (PRIN 2001 and PRIN 2002), and by the Agenzia Spaziale Italiana. I. R. K. and S. G. D. acknowledge the support of STScI grants GO-6095, 7470, 8118, and 8723.
Funding AgencyGrant Number
NASANAS 5-26555
Ministero dell'Istruzione, dell'Università e della Ricerca (MIUR)PRIN 2001
Ministero dell'Istruzione, dell'Università e della Ricerca (MIUR)PRIN 2002
Agenzia Spaziale Italiana (ASI)UNSPECIFIED
Space Telescope Science InstituteUNSPECIFIED
Subject Keywords:blue stragglers — globular clusters: general — Hertzsprung-Russell diagram — stars: luminosity function, mass function
Issue or Number:2
Record Number:CaltechAUTHORS:20191002-155149117
Persistent URL:
Official Citation:Giampaolo Piotto et al 2004 ApJ 604 L109
Usage Policy:No commercial reproduction, distribution, display or performance rights in this work are provided.
ID Code:99035
Deposited By: Tony Diaz
Deposited On:02 Oct 2019 23:02
Last Modified:16 Nov 2021 17:43

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