Rediscovery of the Sixth Star Cluster in the Fornax Dwarf Spheroidal Galaxy
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.
- Research Organization:
- SLAC National Accelerator Laboratory (SLAC), Menlo Park, CA (United States); Univ. of Michigan, Ann Arbor, MI (United States); Oak Ridge National Laboratory (ORNL), Oak Ridge, TN (United States); Fermi National Accelerator Laboratory (FNAL), Batavia, IL (United States)
- Sponsoring Organization:
- USDOE Office of Science (SC), High Energy Physics (HEP); National Science Foundation (NSF); USDOE Office of Science (SC), Advanced Scientific Computing Research (ASCR)
- Contributing Organization:
- DES Collaboration
- Grant/Contract Number:
- AC02-76SF00515; AC02-07CH11359; AC05-00OR22725; AST-1813881; AST-1138766; AST- 1536171; AYA2015-71825; ESP2015-66861; FPA2015-68048; SEV- 2016-0588; SEV-2016-0597; MDM-2015-0509; SC0019193
- OSTI ID:
- 1526932
- Alternate ID(s):
- OSTI ID: 1531224; OSTI ID: 1546032; OSTI ID: 1726010
- Report Number(s):
- arXiv:1902.04589; FERMILAB-PUB-19-195-AE-CD
- Journal Information:
- The Astrophysical Journal. Letters (Online), Vol. 875, Issue 2; ISSN 2041-8213
- Publisher:
- Institute of Physics (IOP)Copyright Statement
- Country of Publication:
- United States
- Language:
- English
Web of Science
Embedding globular clusters in dark matter minihaloes solves the cusp–core and timing problems in the Fornax dwarf galaxy
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journal | January 2020 |
An old, metal-poor globular cluster in Sextans A and the metallicity floor of globular cluster systems
|
journal | May 2019 |
Globular clusters as probes of dark matter cusp-core transformations
|
journal | June 2019 |
Globular clusters as probes of dark matter cusp-core transformations | text | January 2019 |
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