Rediscovery of the Sixth Star Cluster in the Fornax Dwarf Spheroidal Galaxy. (arXiv:1902.04589v1 [astro-ph.GA])

Rediscovery of the Sixth Star Cluster in the Fornax Dwarf Spheroidal Galaxy. (arXiv:1902.04589v1 [astro-ph.GA])
<a href="http://arxiv.org/find/astro-ph/1/au:+Wang_M/0/1/0/all/0/1">Mei-Yu Wang</a>, <a href="http://arxiv.org/find/astro-ph/1/au:+Koposov_S/0/1/0/all/0/1">Sergey Koposov</a>, <a href="http://arxiv.org/find/astro-ph/1/au:+Drlica_Wagner_A/0/1/0/all/0/1">Alex Drlica-Wagner</a>, <a href="http://arxiv.org/find/astro-ph/1/au:+Pieres_A/0/1/0/all/0/1">Adriano Pieres</a>, <a href="http://arxiv.org/find/astro-ph/1/au:+Li_T/0/1/0/all/0/1">Ting Li</a>, <a href="http://arxiv.org/find/astro-ph/1/au:+Boer_T/0/1/0/all/0/1">Thomas de Boer</a>, <a href="http://arxiv.org/find/astro-ph/1/au:+Bechtol_K/0/1/0/all/0/1">Keith Bechtol</a>, <a href="http://arxiv.org/find/astro-ph/1/au:+Belokurov_V/0/1/0/all/0/1">Vasily Belokurov</a>, <a href="http://arxiv.org/find/astro-ph/1/au:+Pace_A/0/1/0/all/0/1">A. B. Pace</a>, <a href="http://arxiv.org/find/astro-ph/1/au:+Abbott_T/0/1/0/all/0/1">T. M. C. Abbott</a>, <a href="http://arxiv.org/find/astro-ph/1/au:+Annis_J/0/1/0/all/0/1">J. Annis</a>, <a href="http://arxiv.org/find/astro-ph/1/au:+Bertin_E/0/1/0/all/0/1">E. Bertin</a>, <a href="http://arxiv.org/find/astro-ph/1/au:+Brooks_D/0/1/0/all/0/1">D. Brooks</a>, <a href="http://arxiv.org/find/astro-ph/1/au:+Buckley_Geer_E/0/1/0/all/0/1">E. Buckley-Geer</a>, <a href="http://arxiv.org/find/astro-ph/1/au:+Burke_D/0/1/0/all/0/1">D. L. Burke</a>, <a href="http://arxiv.org/find/astro-ph/1/au:+Rosell_A/0/1/0/all/0/1">A. Carnero Rosell</a>, <a href="http://arxiv.org/find/astro-ph/1/au:+Kind_M/0/1/0/all/0/1">M. Carrasco Kind</a>, <a href="http://arxiv.org/find/astro-ph/1/au:+Carretero_J/0/1/0/all/0/1">J. Carretero</a>, <a href="http://arxiv.org/find/astro-ph/1/au:+Costa_L/0/1/0/all/0/1">L. N. da Costa</a>, <a href="http://arxiv.org/find/astro-ph/1/au:+Vicente_J/0/1/0/all/0/1">J. De Vicente</a>, <a href="http://arxiv.org/find/astro-ph/1/au:+Desai_S/0/1/0/all/0/1">S. Desai</a>, <a href="http://arxiv.org/find/astro-ph/1/au:+Diehl_H/0/1/0/all/0/1">H. T. Diehl</a>, <a href="http://arxiv.org/find/astro-ph/1/au:+Doel_P/0/1/0/all/0/1">P. Doel</a>, <a href="http://arxiv.org/find/astro-ph/1/au:+Estrada_J/0/1/0/all/0/1">J. Estrada</a>, <a href="http://arxiv.org/find/astro-ph/1/au:+Flaugher_B/0/1/0/all/0/1">B. Flaugher</a>, <a href="http://arxiv.org/find/astro-ph/1/au:+Fosalba_P/0/1/0/all/0/1">P. Fosalba</a>, <a href="http://arxiv.org/find/astro-ph/1/au:+Frieman_J/0/1/0/all/0/1">J. Frieman</a>, <a href="http://arxiv.org/find/astro-ph/1/au:+Garcia_Bellido_J/0/1/0/all/0/1">J. Garcia-Bellido</a>, <a href="http://arxiv.org/find/astro-ph/1/au:+Gerdes_D/0/1/0/all/0/1">D. W. Gerdes</a>, <a href="http://arxiv.org/find/astro-ph/1/au:+Gruen_D/0/1/0/all/0/1">D. Gruen</a>, <a href="http://arxiv.org/find/astro-ph/1/au:+Gruendl_R/0/1/0/all/0/1">R. A. Gruendl</a>, <a href="http://arxiv.org/find/astro-ph/1/au:+Gschwend_J/0/1/0/all/0/1">J. Gschwend</a>, <a href="http://arxiv.org/find/astro-ph/1/au:+Gutierrez_G/0/1/0/all/0/1">G. Gutierrez</a>, <a href="http://arxiv.org/find/astro-ph/1/au:+Hollowood_D/0/1/0/all/0/1">D. L. Hollowood</a>, <a href="http://arxiv.org/find/astro-ph/1/au:+Honscheid_K/0/1/0/all/0/1">K. Honscheid</a>, <a href="http://arxiv.org/find/astro-ph/1/au:+Hoyle_B/0/1/0/all/0/1">B. Hoyle</a>, <a href="http://arxiv.org/find/astro-ph/1/au:+James_D/0/1/0/all/0/1">D. J. James</a>, <a href="http://arxiv.org/find/astro-ph/1/au:+Kent_S/0/1/0/all/0/1">S. Kent</a>, <a href="http://arxiv.org/find/astro-ph/1/au:+Kuehn_K/0/1/0/all/0/1">K. Kuehn</a>, <a href="http://arxiv.org/find/astro-ph/1/au:+Kuropatkin_N/0/1/0/all/0/1">N. Kuropatkin</a>, <a href="http://arxiv.org/find/astro-ph/1/au:+Maia_M/0/1/0/all/0/1">M. A. G. Maia</a>, <a href="http://arxiv.org/find/astro-ph/1/au:+Marshall_J/0/1/0/all/0/1">J. L. Marshall</a>, <a href="http://arxiv.org/find/astro-ph/1/au:+Menanteau_F/0/1/0/all/0/1">F. Menanteau</a>, <a href="http://arxiv.org/find/astro-ph/1/au:+Miquel_R/0/1/0/all/0/1">R. Miquel</a>, <a href="http://arxiv.org/find/astro-ph/1/au:+Plazas_A/0/1/0/all/0/1">A. A. Plazas</a>, <a href="http://arxiv.org/find/astro-ph/1/au:+Sanchez_E/0/1/0/all/0/1">E. Sanchez</a>, <a href="http://arxiv.org/find/astro-ph/1/au:+Santiago_B/0/1/0/all/0/1">B. Santiago</a>, <a href="http://arxiv.org/find/astro-ph/1/au:+Scarpine_V/0/1/0/all/0/1">V. Scarpine</a>, <a href="http://arxiv.org/find/astro-ph/1/au:+Schindler_R/0/1/0/all/0/1">R. Schindler</a>, <a href="http://arxiv.org/find/astro-ph/1/au:+Schubnell_M/0/1/0/all/0/1">M. Schubnell</a>, <a href="http://arxiv.org/find/astro-ph/1/au:+Serrano_S/0/1/0/all/0/1">S. Serrano</a>, <a href="http://arxiv.org/find/astro-ph/1/au:+Sevilla_Noarbe_I/0/1/0/all/0/1">I. Sevilla-Noarbe</a>, <a href="http://arxiv.org/find/astro-ph/1/au:+Smith_M/0/1/0/all/0/1">M. Smith</a>, <a href="http://arxiv.org/find/astro-ph/1/au:+Smith_R/0/1/0/all/0/1">R. C. Smith</a>, <a href="http://arxiv.org/find/astro-ph/1/au:+Sobreira_F/0/1/0/all/0/1">F. Sobreira</a>, <a href="http://arxiv.org/find/astro-ph/1/au:+Suchyta_E/0/1/0/all/0/1">E. Suchyta</a>, <a href="http://arxiv.org/find/astro-ph/1/au:+Swanson_M/0/1/0/all/0/1">M. E. C. Swanson</a>, <a href="http://arxiv.org/find/astro-ph/1/au:+Tarle_G/0/1/0/all/0/1">G. Tarle</a>, <a href="http://arxiv.org/find/astro-ph/1/au:+Thomas_D/0/1/0/all/0/1">D. Thomas</a>, et al. (2 additional authors not shown)

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.

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