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Published November 1, 2016 | Published + Submitted
Journal Article Open

The Next Generation Virgo cluster Survey (NGVS). XXV. Fiducial panchromatic colors of Virgo core globular clusters and their comparison to model predictions


The central region of the Virgo Cluster of galaxies contains thousands of globular clusters (GCs), an order of magnitude more than the number of clusters found in the Local Group. Relics of early star formation epochs in the universe, these GCs also provide ideal targets to test our understanding of the spectral energy distributions (SEDs) of old stellar populations. Based on photometric data from the Next Generation Virgo Cluster Survey (NGVS) and its near-infrared counterpart NGVS-IR, we select a robust sample of ≈ 2000 GCs with excellent photometry and that span the full range of colors present in the Virgo core. The selection exploits the well-defined locus of GCs in the uiK diagram and the fact that the GCs are marginally resolved in the images. We show that the GCs define a narrow sequence in five-dimensional color space, with limited but real dispersion around the mean sequence. The comparison of these SEDs with the predictions of 11 widely used population synthesis models highlights differences between the models and also shows that no single model adequately matches the data in all colors. We discuss possible causes for some of these discrepancies. Forthcoming papers of this series will examine how best to estimate photometric metallicities in this context, and compare the Virgo GC colors with those in other environments.

Additional Information

© 2016 American Astronomical Society. Received 2016 June 23. Accepted 2016 August 2. Published 2016 November 18. The authors gratefully acknowledge fruitful discussions with M. Betoule, N. Regnault, H. J. McCracken, R. Peletier, R. Ibata, N. Martin, A. Nebot, E. Schlafly, P. Prugniel, and S. C. Trager. Direct information on some model details was kindly provided by C. Maraston, S. Charlot, G. Bruzual, A. Vazdekis, and L. Girardi. This work was supported in part by the French Agence Nationale de la Recherche (ANR) grant Programme Blanc VIRAGE (ANR10-BLANC-0506-01), by the French-Chilean Collaboration Program ECOS Sud-CONICYT under grant C15U02, by the Programme National Cosmologie & Galaxies (PNCG 2016), and by the Canadian Advanced Network for Astronomical Research (CANFAR), which has been made possible by funding from CANARIE under the Network-Enabled Platforms program. T. H. P. acknowledges support by FONDECYT Regular Project No. 1161817 and BASAL Center for Astrophysics and Associated Technologies (PFB-06). This research also used the facilities of the Canadian Astronomy Data Centre operated by the National Research Council of Canada with the support of the Canadian Space Agency. E.W.P. acknowledges support from the National Natural Science Foundation of China under Grant No. 11573002, and from the Strategic Priority Research Program, "The Emergence of Cosmological Structures," of the Chinese Academy of Sciences, Grant No. XDB09000105. C.L. acknowledges the National Key Basic Research Program of China (2015CB857002), NSFC grants 11203017 and 11125313. E.T. acknowledges the NSF grants AST-1412504 and AST-1010039. Funding for SDSS-III has been provided by the Alfred P. Sloan Foundation, the Participating Institutions, the National Science Foundation, and the U.S. Department of Energy Office of Science. The SDSS-III website is http://www.sdss3.org/. SDSS-III is managed by the Astrophysical Research Consortium for the Participating Institutions of the SDSS-III Collaboration, including the University of Arizona, the Brazilian Participation Group, Brookhaven National Laboratory, Carnegie Mellon University, University of Florida, the French Participation Group, the German Participation Group, Harvard University, the Instituto de Astrofisica de Canarias, the Michigan State/Notre Dame/JINA Participation Group, Johns Hopkins University, Lawrence Berkeley National Laboratory, Max Planck Institute for Astrophysics, Max Planck Institute for Extraterrestrial Physics, New Mexico State University, New York University, Ohio State University, Pennsylvania State University, University of Portsmouth, Princeton University, the Spanish Participation Group, University of Tokyo, University of Utah, Vanderbilt University, University of Virginia, University of Washington, and Yale University. This work is based in part on data obtained as part of the UKIRT Infrared Deep Sky Survey. This research has made use of the VizieR catalog access tool and the Aladin plot tool at CDS, Strasbourg, France, as well as the TOPCAT software available at http://www.starlink.ac.uk/topcat/.

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