J/ApJ/875/L13 DECam r and i magnitudes in the Fornax 6 cluster (Wang+, 2019)
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.,
Carrasco Kind M., 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., Gruen D., Gruendl R.A., Gschwend J.,
Gutierrez G., Hollowood D.L., Honscheid K., Hoyle B., James D.J., Kent S.,
Kuehn 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.,
Walker A.R. (The DES Collaboration).
<Astrophys. J., 875, L13 (2019)>
=2019ApJ...875L..13W 2019ApJ...875L..13W
ADC_Keywords: Photometry, RI; Clusters, globular
Keywords: galaxies: star clusters: general
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.
Description:
We found that the area around Fornax 6 was observed in r and i bands
during exceptional seeing conditions of 0.6"-0.7" by a Dark Energy
Camera (DECam) program 2016B-0244 (PI: B. Tucker) that is available in
the NOAO Science Archive.
See Section 2 for further explanations.
Objects:
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RA (ICRS) DE Designation(s)
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02 40 06.90 -34 25 19.2 Fornax 6 = NAME Cluster 6 in Fornax
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File Summary:
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FileName Lrecl Records Explanations
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ReadMe 80 . This file
fig3.dat 44 8687 Fornax 6 positions and r and i magnitudes
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Description of file:
for6_daophot.FITS also available on the FTP Section is the original
FITS file for the "data behind Figure 3" given in the paper.
See also:
II/350 : VLT Survey Telescope ATLAS (Shanks+, 2015)
II/357 : The Dark Energy Survey (DES): Data Release 1 (Abbott+, 2018)
I/345 : Gaia DR2 (Gaia Collaboration, 2018)
VII/195 : Globular Clusters in the Milky Way (Harris, 1996)
VII/202 : Globular Clusters in the Milky Way (Harris, 1997)
J/PASP/110/533 : BR photometry of Fornax bright stars (Stetson+ 1998)
J/ApJS/161/304 : Star clusters in the MW and satellites (McLaughlin+, 2005)
J/A+A/459/423 : VI and [Fe/H] of Fornax dSph RGB stars (Battaglia+, 2006)
J/AJ/137/3100 : Radial velocities of 4 dSph galaxies (Walker+, 2009)
J/AJ/144/4 : Dwarf galaxies in the Local Group (McConnachie+, 2012)
J/MNRAS/453/690 : Fornax VST ATLAS catalogue (Bate+, 2015)
Byte-by-byte Description of file: fig3.dat
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Bytes Format Units Label Explanations
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1- 12 F12.9 deg RAdeg Right ascension (J2000)
14- 26 F13.9 deg DEdeg Declination (J2000)
28- 35 F8.5 mag rmag [15.6/30.6] CTIO/DECam r band (AB) magnitude
37- 44 F8.5 mag imag [16.5/29.5] CTIO/DECam i band (AB) magnitude
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History:
From electronic version of the journal
(End) Prepared by [AAS], Emmanuelle Perret [CDS] 22-Sep-2020