The globular cluster relative ages and the milky way formation time scale

Antonio Aparicio, Antonio Marín-Franch, Giampaolo Piotto, Alfred Rosenberg, Brian Chaboyer, Ata Sarajedini, Michael Hiram Siegel, Jay Anderson, Luigi R. Bedin, Aaron Dotter, Maren Hempel, Ivan King, Steven Majewski, Antonino P. Milone, Nathaniel Paust, I. Neill Reid

Research output: Chapter in Book/Report/Conference proceedingConference contribution

Abstract

The ACS Survey of Galactic Globular Clusters is a Hubble Space Telescope (HST) Treasury program designed to provide a new large, deep and homogeneous photometric database. Based on observations from this program, we have measured precise relative ages for a sample of 64 Galactic globular clusters by comparing the relative position of the clusters' main sequence turn offs, using main-sequence fitting to cross-compare clusters within the sample. This method provides relative ages to a formal precision of 2-7%. We demonstrate that the calcidated relative ages are independent of the choice of theoretical model. We find that the Galactic globidar cluster sample can be divided into two groups - a popidation of old clusters with an intrinsic age dispersion of -̃ 3% and no age-metallicity relation, and a group of younger clusters with an age-metaUicity relation similar to that of the globular clusters associated with the Sagittarius dwarf galaxy. These results are consistent with the Milky Way halo having formed in two phases. The first phase would be compatible with a rapid (<0.8 Gyr) assembling process of the halo, in which the clusters in the old group were formed. The second phase lasted much longer in time and resulted in a group of globidar clusters with a clear age-metallicity relation. It is very tempting to argue that the origin of this second group of clusters is related to the accretion of Milky Way satelUte galaxies, but the origin of the age-metallicity relation remains unclear.

Original languageEnglish (US)
Title of host publicationProbing Stellar Populations Out To The Distant Universe - Cefalu 2008 - Proceedings of the International Conference
Pages222-229
Number of pages8
DOIs
StatePublished - Jul 21 2009
EventInternational Conference on Probing Stellar Populations Out To The Distant Universe, Cefalu 2008 - Cefalu, Sicily, Italy
Duration: Sep 7 2008Sep 19 2008

Publication series

NameAIP Conference Proceedings
Volume1111
ISSN (Print)0094-243X
ISSN (Electronic)1551-7616

Other

OtherInternational Conference on Probing Stellar Populations Out To The Distant Universe, Cefalu 2008
CountryItaly
CityCefalu, Sicily
Period9/7/089/19/08

All Science Journal Classification (ASJC) codes

  • Ecology, Evolution, Behavior and Systematics
  • Ecology
  • Plant Science
  • Physics and Astronomy(all)
  • Nature and Landscape Conservation

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  • Cite this

    Aparicio, A., Marín-Franch, A., Piotto, G., Rosenberg, A., Chaboyer, B., Sarajedini, A., Siegel, M. H., Anderson, J., Bedin, L. R., Dotter, A., Hempel, M., King, I., Majewski, S., Milone, A. P., Paust, N., & Reid, I. N. (2009). The globular cluster relative ages and the milky way formation time scale. In Probing Stellar Populations Out To The Distant Universe - Cefalu 2008 - Proceedings of the International Conference (pp. 222-229). (AIP Conference Proceedings; Vol. 1111). https://doi.org/10.1063/1.3141548