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

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

doi:10.3847/2041-8213/ab14f5

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

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 CostaJ. 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

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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 ∼6-6.7σ 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.

Original language	English
Article number	L13
Journal	Astrophysical Journal Letters
Volume	875
Issue number	2
DOIs	https://doi.org/10.3847/2041-8213/ab14f5
State	Published - Apr 20 2019

Funding

Funders	Funder number
Seventh Framework Programme	1813881, 1138766, 240672, 306478, 291329

Keywords

galaxies: star clusters: general

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10.3847/2041-8213/ab14f5

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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., Rosell, A. C., Kind, M. C., Carretero, J., ... Walker, A. R. (2019). Rediscovery of the Sixth Star Cluster in the Fornax Dwarf Spheroidal Galaxy. Astrophysical Journal Letters, 875(2), Article L13. https://doi.org/10.3847/2041-8213/ab14f5

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title = "Rediscovery of the Sixth Star Cluster in the Fornax Dwarf Spheroidal Galaxy",

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 ∼6-6.7σ 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.",

keywords = "galaxies: star clusters: general",

author = "Wang, {M. Y.} and S. Koposov and A. Drlica-Wagner and A. Pieres and Li, {T. S.} and {De Boer}, T. and K. Bechtol and V. Belokurov and Pace, {A. B.} and D. Bacon and Abbott, {T. M.C.} and J. Annis and E. Bertin and D. Brooks and E. Buckley-Geer and Burke, {D. L.} and Rosell, {A. Carnero} and Kind, {M. Carrasco} and J. Carretero and {Da Costa}, {L. N.} and {De Vicente}, J. and S. Desai and Diehl, {H. T.} and P. Doel and J. Estrada and B. Flaugher and P. Fosalba and J. Frieman and J. Garc{\'i}a-Bellido and Gerdes, {D. W.} and D. Gruen and Gruendl, {R. A.} and J. Gschwend and G. Gutierrez and Hollowood, {D. L.} and K. Honscheid and B. Hoyle and James, {D. J.} and S. Kent and K. Kuehn and N. Kuropatkin and Maia, {M. A.G.} and Marshall, {J. L.} and F. Menanteau and R. Miquel and Plazas, {A. A.} and E. Sanchez and B. Santiago and V. Scarpine and R. Schindler and M. Schubnell and S. Serrano and I. Sevilla-Noarbe and M. Smith and Smith, {R. C.} and F. Sobreira and E. Suchyta and Swanson, {M. E.C.} and G. Tarle and D. Thomas and Tucker, {D. L.} and Walker, {A. R.}",

year = "2019",

month = apr,

day = "20",

doi = "10.3847/2041-8213/ab14f5",

language = "English",

volume = "875",

journal = "Astrophysical Journal Letters",

issn = "2041-8205",

publisher = "American Astronomical Society",

number = "2",

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Wang, MY, Koposov, S, Drlica-Wagner, A, Pieres, A, Li, TS, De Boer, T, Bechtol, K, Belokurov, V, Pace, AB, Bacon, D, Abbott, TMC, Annis, J, Bertin, E, Brooks, D, Buckley-Geer, E, Burke, DL, Rosell, AC, Kind, MC, Carretero, J, Da Costa, LN, De Vicente, J, Desai, S, Diehl, HT, Doel, P, Estrada, J, Flaugher, B, Fosalba, P, Frieman, J, García-Bellido, J, Gerdes, DW, Gruen, D, Gruendl, RA, Gschwend, J, Gutierrez, G, Hollowood, DL, Honscheid, K, Hoyle, B, James, DJ, Kent, S, Kuehn, K, Kuropatkin, N, Maia, MAG, Marshall, JL, Menanteau, F, Miquel, R, Plazas, AA, Sanchez, E, Santiago, B, Scarpine, V, Schindler, R, Schubnell, M, Serrano, S, Sevilla-Noarbe, I, Smith, M, Smith, RC, Sobreira, F, Suchyta, E, Swanson, MEC, Tarle, G, Thomas, D, Tucker, DL & Walker, AR 2019, 'Rediscovery of the Sixth Star Cluster in the Fornax Dwarf Spheroidal Galaxy', Astrophysical Journal Letters, vol. 875, no. 2, L13. https://doi.org/10.3847/2041-8213/ab14f5

TY - JOUR

T1 - Rediscovery of the Sixth Star Cluster in the Fornax Dwarf Spheroidal Galaxy

AU - Wang, M. Y.

AU - Koposov, S.

AU - Drlica-Wagner, A.

AU - Pieres, A.

AU - Li, T. S.

AU - De Boer, T.

AU - Bechtol, K.

AU - Belokurov, V.

AU - Pace, A. B.

AU - Bacon, D.

AU - Abbott, T. M.C.

AU - Annis, J.

AU - Bertin, E.

AU - Brooks, D.

AU - Buckley-Geer, E.

AU - Burke, D. L.

AU - Rosell, A. Carnero

AU - Kind, M. Carrasco

AU - Carretero, J.

AU - Da Costa, L. N.

AU - De Vicente, J.

AU - Desai, S.

AU - Diehl, H. T.

AU - Doel, P.

AU - Estrada, J.

AU - Flaugher, B.

AU - Fosalba, P.

AU - Frieman, J.

AU - García-Bellido, J.

AU - Gerdes, D. W.

AU - Gruen, D.

AU - Gruendl, R. A.

AU - Gschwend, J.

AU - Gutierrez, G.

AU - Hollowood, D. L.

AU - Honscheid, K.

AU - Hoyle, B.

AU - James, D. J.

AU - Kent, S.

AU - Kuehn, K.

AU - Kuropatkin, N.

AU - Maia, M. A.G.

AU - Marshall, J. L.

AU - Menanteau, F.

AU - Miquel, R.

AU - Plazas, A. A.

AU - Sanchez, E.

AU - Santiago, B.

AU - Scarpine, V.

AU - Schindler, R.

AU - Schubnell, M.

AU - Serrano, S.

AU - Sevilla-Noarbe, I.

AU - Smith, M.

AU - Smith, R. C.

AU - Sobreira, F.

AU - Suchyta, E.

AU - Swanson, M. E.C.

AU - Tarle, G.

AU - Thomas, D.

AU - Tucker, D. L.

AU - Walker, A. R.

PY - 2019/4/20

Y1 - 2019/4/20

N2 - 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 ∼6-6.7σ 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.

AB - 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 ∼6-6.7σ 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.

KW - galaxies: star clusters: general

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U2 - 10.3847/2041-8213/ab14f5

DO - 10.3847/2041-8213/ab14f5

M3 - Article

AN - SCOPUS:85070549439

SN - 2041-8205

VL - 875

JO - Astrophysical Journal Letters

JF - Astrophysical Journal Letters

IS - 2

M1 - L13

ER -

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

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