Rediscovery of the Sixth Star Cluster in the Fornax Dwarf Spheroidal Galaxy

Wang, M. Y.; Koposov, S.; Drlica-Wagner, A.; Pieres, A.; Li, T. S.; de Boer, T.; Bechtol, K.; Belokurov, V.; Pace, A. B.; Bacon, D.; Abbott, T. M. C.; Annis, J.; Bertin, E.; Brooks, D.; Buckley-Geer, E.; Burke, D. L.; Carnero Rosell, A.; Kind, M. Carrasco; Carretero, J.; da Costa, L. N.; De Vicente, J.; Desai, S.; Diehl, H. T.; Doel, P.; Estrada, J.; Flaugher, B.; Fosalba, P.; Frieman, J.; Garcia-Bellido, J.; Gerdes, D. W.; Grün, D.; Gründl, R. A.; Gschwend, J.; Gutierrez, G.; Hollowood, D. L.; Honscheid, K.; Hoyle, B.; James, D. J.; Kent, S.; Kühn, K.; Kuropatkin, N.; Maia, M. A. G.; Marshall, J. L.; Menanteau, F.; Miquel, R.; Plazas, A. A.; Sanchez, E.; Santiago, B.; Scarpine, V.; Schindler, R.; Schubnell, M.; Serrano, S.; Sevilla-Noarbe, I.; Smith, M.; Smith, R. C.; Sobreira, F.; Suchyta, E.; Swanson, M. E. C.; Tarle, G.; Thomas, D.; Tucker, D. L. und Walker, A. R. (2019): Rediscovery of the Sixth Star Cluster in the Fornax Dwarf Spheroidal Galaxy. In: Astrophysical Journal Letters, Bd. 875, Nr. 2, L13

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 similar to 6-6.7 sigma 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.

• Dokumententyp: Zeitschriftenartikel
• Fakultät: Physik
• Themengebiete: 500 Naturwissenschaften und Mathematik > 530 Physik
• ISSN: 2041-8205
• Sprache: Englisch