J/ApJ/923/77 Fornax stars M2FS spectroscopy with Gaia EDR3 data (Pace+, 2021)
Spectroscopic confirmation of the sixth globular cluster in the Fornax dwarf
spheroidal galaxy.
Pace A.B., Walker M.G., Koposov S.E., Caldwell N., Mateo M.,
Olszewski E.W., Bailey III J.I., Wang M.-Y.
<Astrophys. J., 923, 77-77 (2021)>
=2021ApJ...923...77P 2021ApJ...923...77P (SIMBAD/NED BibCode)
ADC_Keywords: Galaxies, dwarf; Abundances; Spectra, optical; Radial velocities
Keywords: Globular star clusters; Dwarf spheroidal galaxies
Abstract:
The Fornax dwarf spheroidal galaxy has an anomalous number of globular
clusters, five, for its stellar mass. There is a longstanding debate
about a potential sixth globular cluster (Fornax 6) that has recently
been "rediscovered" in DECam imaging. We present new Magellan/M2FS
spectroscopy of the Fornax 6 cluster and Fornax dSph. Combined with
literature data we identify ∼15-17 members of the Fornax 6 cluster,
showing that this overdensity is indeed a star cluster and associated
with the Fornax dSph. The cluster is significantly more metal-rich
(mean metallicity of [Fe/H]=-0.71±0.05) than the other five Fornax
globular clusters (-2.5<[Fe/H]<-1.4) and more metal-rich than the
bulk of Fornax. We measure a velocity dispersion of 5.6-1.6+2.0kms-1
corresponding to an anomalously high mass-to-light of 15<M/L<258 at
90% confidence when calculated assuming equilibrium. Two stars inflate
this dispersion and may be either Fornax field stars or as yet
unresolved binary stars. Alternatively, the Fornax 6 cluster may be
undergoing tidal disruption. Based on its metal-rich nature, the
Fornax 6 cluster is likely younger than the other Fornax clusters,
with an estimated age of ∼2Gyr when compared to stellar isochrones.
The chemodynamics and star formation history of Fornax shows imprints
of major events such as infall into the Milky Way, multiple pericenter
passages, star formation bursts, and/or potential mergers or
interactions. Any of these events may have triggered the formation of
the Fornax 6 cluster.
Description:
We present results from new spectroscopic observations of Fornax stars
that we obtained using the Michigan/Magellan Fiber System (M2FS) at
the 6.5m Magellan/Clay Telescope at Las Campanas Observatory, Chile.
We used a configuration that covered the approximate range 5130-5190Å
at resolution R∼24000. Between the years 2018 and 2020, we observed 8
Fornax fields with M2FS.
We include additional Magellan/MIKE Fiber System (MMFS) spectroscopic
data from Walker+ 2009, J/AJ/137/3100 which increases the number of
Fornax members by ∼2400 stars.
Objects:
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RA (ICRS) DE Designation(s)
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02 39 59.29 -34 26 56.9 Fornax = NAME Fornax Dwarf Spheroidal
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File Summary:
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FileName Lrecl Records Explanations
--------------------------------------------------------------------------------
ReadMe 80 . This file
table2.dat 155 980 M2FS stellar spectroscopy of Fornax
table3.dat 107 3210 Combined MMFS and M2FS catalog of Fornax
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See also:
VII/202 : Globular Clusters in the Milky Way (Harris, 1997)
II/357 : The Dark Energy Survey (DES): Data Release 1 (Abbott+, 2018)
I/350 : Gaia EDR3 (Gaia Collaboration, 2020)
J/PASP/110/533 : BR photometry of Fornax bright stars (Stetson+ 1998)
J/ApJ/521/577 : HST studies of the WLM globular cluster (Hodge+, 1999)
J/AJ/132/781 : 2MASS colors of Magellanic cloud star clusters (Pessev+, 2006)
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/A+A/523/A17 : Individual stars in Fornax dSph center (Letarte+, 2010)
J/ApJS/191/352 : Abundances in stars of MW dwarf satellites (Kirby+, 2010)
J/A+A/538/A100 : Abundances red giants in Carina dSph (Lemasle+, 2012)
J/ApJ/779/102 : Metallicities of RGB stars in dwarf galaxies (Kirby+, 2013)
J/A+A/572/A82 : Abundances in outer parts of Fornax dSph (Hendricks+, 2014)
J/MNRAS/448/2717 : Bayesian analysis of resolved stellar sp. (Walker+, 2015)
J/ApJ/808/108 : M2FS stellar spectroscopy of Reticulum 2 (Walker+, 2015)
J/A+A/585/A86 : Fornax dSph H4 globular cluster stars (Hendricks+, 2016)
J/ApJ/817/41 : Abundances of 4 metal-poor red giants in BooII (Ji+, 2016)
J/ApJ/819/53 : Magellan/M2FS sp. of Tucana 2 and Grus 1 (Walker+, 2016)
J/ApJ/829/26 : Variable stars in Andromeda XXV field. III. (Cusano+, 2016)
J/ApJ/837/54 : Variable stars in DDO 216-A1 (Cole+, 2017)
J/ApJ/838/83 : RVs, abundances & membership in TriII (Kirby+, 2017)
J/A+A/616/A12 : Gaia DR2 sources in GC and dSph (Gaia Collaboration+, 2018)
J/ApJ/866/22 : Spectroscopic analysis of Tuc III stream (Li+, 2018)
J/ApJ/875/77 : Proper motions of MW satellites with Gaia & DES (Pace+, 2019)
J/ApJ/875/L13 : DECam r and i magnitudes in the Fornax 6 cluster (Wang+, 2019)
J/A+A/626/A15 : Sculptor Red Giant Branch stars abundances (Hill+, 2019)
J/MNRAS/490/3508 : The Southern Stellar Stream Sp. Survey (S5) (Li+, 2019)
J/A+A/635/A107 : Spectroscopy of the Eri 2 cluster (Zoutendijk+, 2020)
J/A+A/638/A104 : Gaia DR2 cand. RR Lyrae of Sgr stream & dwarf (Ramos+, 2020)
J/A+A/642/A176 : Chemical evolution of dSph galaxy Sextans (Theler+, 2020)
J/ApJ/908/18 : HST stellar photometry of Eridanus II (Simon+, 2021)
J/A+A/649/A3 : Gaia EDR3 photometric passbands (Riello+, 2021)
Byte-by-byte Description of file: table2.dat
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Bytes Format Units Label Explanations
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1- 19 I19 --- Gaia Gaia EDR3 identifier
21- 29 F9.6 deg RAdeg [38.57/41.3] Right Ascension (J2000)
31- 40 F10.6 deg DEdeg [-35.6/-33.6] Declination (J2000)
42- 52 F11.3 d HJD Heliocentric Julian Date
54- 58 F5.2 --- S/N [0.27/43.3] Signal-to-Noise ratio
60- 67 F8.2 km/s VLOS [-2452/371.4] Line-of-sight velocity
69- 72 F4.2 km/s e_VLOS [0.6/4.8] Uncertainty in VLOS
74- 79 F6.2 km/s VLOS-Sk [-49.4/96] Skewness measure in VLOS
81- 88 F8.2 km/s VLOS-Ku [-0.7/11167] Kurtosis measure in VLOS
90- 93 I4 K Teff [4007/7967] Effective temperature
95- 98 I4 K e_Teff [6/1019] Uncertainty in Teff
100- 104 F5.2 K Teff-Sk [-5.2/4.7] Skewness measure in Teff
106- 110 F5.2 K Teff-Ku [-1.1/72.2] Kurtosis measure in Teff
112- 115 F4.2 [cm/s2] log(g) [0.03/4.91] Log surface gravity
117- 120 F4.2 [cm/s2] e_log(g) [0.02/1.6] Uncertainty in log(g)
122- 126 F5.2 [cm/s2] log(g)-Sk [-5.1/4.2] Skewness measure in log(g)
128- 132 F5.2 [cm/s2] log(g)-Ku [-1.3/76] Kurtosis measure in log(g)
134- 138 F5.2 [Sun] Z [-3.3/0.8] Metallicity
140- 143 F4.2 [Sun] e_Z [0.05/1.1] Uncertainty in Z
145- 149 F5.2 [Sun] Z-Sk [-4/1.7] Skewness measure in Z
151- 155 F5.2 [Sun] Z-Ku [-1/18] Kurtosis measure in Z
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Byte-by-byte Description of file: table3.dat
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Bytes Format Units Label Explanations
--------------------------------------------------------------------------------
1- 19 I19 --- Gaia Gaia EDR3 identifier
21- 29 F9.6 deg RAdeg [38.57/41.3] Gaia EDR3 Right Ascension (J2000)
31- 40 F10.6 deg DEdeg [-35.6/-33.6] Gaia EDR3 Declination (J2000)
42 I1 --- NVLOS [1/6] Number of VLOS measurements
44 I1 --- NM2FS [0/3] Number of VLOS measurements in M2FS catalog
46- 52 F7.2 km/s VLOS [-268/417] Line-of-sight velocity
54- 58 F5.2 km/s e_VLOS [0.3/17] Uncertainty in VLOS
60- 65 F6.2 [Sun] Z [-3.1/1]?=-99 Metallicity
67- 71 F5.2 [Sun] e_Z [0.05/1.3]?=-9 Uncertainty in Z
73- 77 F5.3 --- Pdsph [0/1] Dwarf Spheroidal membership probability
79- 83 F5.3 --- b_Pdsph [0/1] Lower 16% uncertainty in Pdsph
85- 89 F5.3 --- B_Pdsph [0/1] Upper 84% uncertainty in Pdsph
91- 95 F5.3 --- Pf6 [0/0.995] Fornax 6 globular cluster probability
97- 101 F5.3 --- b_Pf6 [0/0.992] Lower 16% uncertainty in Pf6
103- 107 F5.3 --- B_Pf6 [0/0.997] Upper 84% uncertainty in Pf6
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History:
From electronic version of the journal
(End) Prepared by [AAS], Emmanuelle Perret [CDS] 17-May-2023