Rediscovery of the sixth Star Cluster in the Fornax dwarf spheroidal galaxy
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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 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 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 globular clusters 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.
Original language | English |
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Article number | L13 |
Journal | Astrophysical Journal Letters |
Volume | 875 |
Issue number | 2 |
DOIs | |
Publication status | Published - 16 Apr 2019 |
Documents
- Rediscovery of the Sixth Star Cluster
Rights statement: M. Y. Wang et al 2019 ApJL 875 L13. © 2019. The American Astronomical Society. All rights reserved. Reproduced by permission of the AAS.
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