Year: 2019
Type: article
Abstract: Since first noticed by Shapley in 1939, a faint object coincident with the Fornax dwarf spheroidal has long been discussed as a possible sixth globular cluster (GC) system. However, debate has continued over whether this overdensity is a statistical artifact or a blended galaxy group. In this Letter we demonstrate, using deep DECam imaging data, that this object is well resolved into stars and is a bona fide star cluster. The stellar overdensity of this cluster is statistically significant at the level of ∼6–6.7 σ in several different photometric catalogs including Gaia . Therefore, it is highly unlikely to be caused by random fluctuation. We show that Fornax 6 is a star cluster with a peculiarly low surface brightness and irregular shape, which may indicate a strong tidal influence from its host galaxy. The Hess diagram of Fornax 6 is largely consistent with that of Fornax field stars, but it appears to be slightly bluer. However, it is still likely more metal-rich than most of the GCs in the system. Faint clusters like Fornax 6 that orbit and potentially get disrupted in the centers of dwarf galaxies can prove crucial for constraining the dark matter distribution in Milky Way satellites.
Authors: M. Y. Wang, S. Koposov, A. Drlica-Wagner, A. Pieres, T. S. Li, T. de Boer, K. Bechtol, V. Belokurov, A. B. Pace, D. Bacon, T. M. C. Abbott, J. Annis, E. Bertin, D. Brooks, E. Buckley-Geer, D. L. Burke, A. Carnero Rosell, M. Carrasco Kind, J. Carretero, L. N. da Costa, J. De Vicente, S. Desai, H. T. Diehl, P. Doel, J. Estrada, B. Flaugher, P. Fosalba, J. Frieman, J. García-Bellido, D. W. Gerdes, D. Gruen, R. A. Gruendl, J. Gschwend, G. Gutierrez, D. L. Hollowood, K. Honscheid, B. Hoyle, D. J. James, S. Kent, K. Kuehn, N. Kuropatkin, M. A. G. Maia, J. L. Marshall, F. Menanteau, R. Miquel, A. A. Plazas, E. Sanchez, B. Santiago, V. Scarpine, R. Schindler, M. Schubnell, S. Serrano, I. Sevilla-Noarbe, M. Smith, R. C. Smith, F. Sobreira, E. Suchyta, M. E. C. Swanson, G. Tarle, D. Thomas, D. L. Tucker, A. R. Walker
Institutions: Carnegie Mellon University, University of Cambridge, Fermi National Accelerator Laboratory, University of Chicago, National Observatory, Laboratório Interinstitucional de e-Astronomia, University of Wisconsin–Madison, Large Synoptic Survey Telescope Corporation, Texas A&M University, University of Portsmouth, Cerro Tololo Inter-American Observatory, Centre National de la Recherche Scientifique, Institut d'Astrophysique de Paris, Université Pierre-et-Marie-Curie, University College London, SLAC National Accelerator Laboratory, Kavli Institute for Particle Astrophysics and Cosmology, Stanford University, Centro de Investigaciones Energéticas, Medioambientales y Tecnológicas, University of Illinois Urbana-Champaign, National Center for Supercomputing Applications, Institute for High Energy Physics, Barcelona Institute of Science and Technology, Indian Institute of Technology Hyderabad, Institute of Space Sciences, Institut d'Estudis Espacials de Catalunya, Instituto de Física Teórica, Universidad Autónoma de Madrid, University of Michigan, University of California, Santa Cruz, The Ohio State University, Max Planck Institute for Extraterrestrial Physics, Ludwig-Maximilians-Universität München, Center for Astrophysics Harvard & Smithsonian, Australian Astronomical Optics, Institució Catalana de Recerca i Estudis Avançats, Princeton University, Universidade Federal do Rio Grande do Sul, University of Southampton, Universidade Estadual de Campinas (UNICAMP), Oak Ridge National Laboratory
Language: English
Subfield: Astronomy and Astrophysics
Field: Physics and Astronomy
Domain: Physical Sciences
Open Access status: bronze
Funders: National Science Foundation, U.S. Department of Energy, University of California, Santa Cruz, University of Pennsylvania, Ohio State University, University of Portsmouth, National Centre for Supercomputing Applications, Centres de Recerca de Catalunya, University College London, European Commission, University of Sussex, Deutsche Forschungsgemeinschaft, Generalitat de Catalunya, Eidgenössische Technische Hochschule Zürich, Ministerio de Economía y Competitividad, Conselho Nacional de Desenvolvimento Científico e Tecnológico, Fundação Carlos Chagas Filho de Amparo à Pesquisa do Estado do Rio de Janeiro, Financiadora de Estudos e Projetos, Ministerio de Ciencia e Innovación, ARC Centre of Excellence for All-Sky Astrophysics, Institut de Física d'Altes Energies, University of Illinois at Urbana-Champaign, Office of Science, Center for Cosmology and Astroparticle Physics, Ohio State University, Kavli Institute for Cosmological Physics, University of Chicago, Science and Technology Facilities Council, European Regional Development Fund, Centro de Investigaciones Energéticas, Medioambientales y Tecnológicas, High Energy Physics, Integrated Electronics Engineering Center, Binghamton University, Argonne National Laboratory, Fermilab, Lawrence Berkeley National Laboratory, FP7 Ideas: European Research Council, SLAC National Accelerator Laboratory
Awards: G1054097061, G1265542407, Capitalizing on Gravitational Shear, G1294705454, G1313983767, G1328166135, G1491530973, G154696372, Testing the Dark Energy Paradigm and Measuring Neutrino Mass with the Dark Energy Survey, G1635920164, G1750188476, PROPOSAL TO EXPLORE THE FUNDAMENTAL CONSTITUENTS OF THE UNIVERSE FUNDING YEARS FY 2018-2020, G1907584174, G1993551506, G2401681081, G2409381996, G2560588496, G265847165, G2792165588, G3154116105, G3207356259, G3467815775, G3485823607, G3523651922, G3715052068, G373470904, The Dark Energy Survey Data Management Operations, G3870743921, G393177772, G3965623739, G3968781304, G4104599821, G4334057779, G4404904460, G4478587286, G454676879, Understanding the Origin of Cosmic Structure, G4760961572, G4960654128, G496129201, G498139845, G5051949629, G5202711728, G5417015564, G5616713406, Astronomy Observation and Theory Consolidated Grant 2016-2019, G5702163051, G585908603, G6242770028, G6480793128, G6514847661, G6676276723, G7038324121, G716412294, Collaborative Research: Dark Matter and Substructure in the Galactic Halo with Gaia and Multi-Object Spectroscopy, G7290792616, G7310333339, G7711421660, G7788408655, G7835623888, G7954596376, Collaborative Research: The Dark Energy Survey Data Management Operations, G86560745, G969889393
OpenAlex ID: W2912066367