J/A+A/683/A167 5 recently discov. globular clusters MUSE analysis (Gran+, 2024)
The treasure behind the haystack:
MUSE analysis of five recently discovered globular clusters.
Gran F., Kordopatis G., Zoccali M., Hill V., Saviane I., Navarrete C.,
Rojas-Arriagada A., Carballo-Bello J., Hartke J., Valenti E.,
Contreras Ramos R., De Leo M., Fabbro S.
<Astron. Astrophys., 683, A167 (2024)>
=2024A&A...683A.167G 2024A&A...683A.167G (SIMBAD/NED BibCode)
ADC_Keywords: Milky Way ; Clusters, globular ; Radial velocities ;
Effective temperatures ; Abundances, [Fe/H]; Optical
Keywords: surveys - reference systems - stars: kinematics and dynamics -
Galaxy: bulge - globular clusters: general - Galaxy: halo
Abstract:
After the second data release of Gaia, the number of new globular
cluster candidates has increased significantly. However, most of them
need to be properly characterised, both spectroscopically and
photometrically, by means of radial velocities, metallicities, and
deeper photometric observations.
Our goal is to provide an independent confirmation of the cluster
nature of Gran 4, a recently discovered globular cluster, with
follow-up spectroscopic observations. The derived radial velocity for
individual stars, coupled with proper motions, allows us to isolate
cluster members from field stars, while the analysis of their spectra
allows us to derive metallicities. By including in the analysis the
recently confirmed clusters Gran 1, 2, 3, and 5, we aim to completely
characterise recently discovered globular clusters.
Using Gaia DR3 and VVV catalogue data and MUSE at VLT observations, we
selected cluster members based on their proper motions, radial
velocities and their position in colour-magnitude diagrams.
Furthermore, full spectral synthesis was performed on the cluster
members, extracting surface parameters and metallicity from MUSE
spectra. Finally, a completeness estimation was performed on the total
globular cluster population of the Milky Way.
We confirm the nature of Gran 4, a newly discovered globular cluster
behind the Galactic bulge, with a mean radial velocity of
RV=-265.28±3.92km/s and a mean metallicity of
[Fe/H]=-1.72±0.32dex. Additionally, independent measurements of the
metallicities were derived for Gran 1, 2, 3, and 5. We also revise the
observational lower mass limit for a globular cluster to survive in
the bulge and disc environment. We estimate that ∼12-26 globular
clusters have still to be discovered on the other side of the Galaxy
(i.e., behind the bulge, bar and disk), up to 20kpc.
Description:
We used the Gaia Data Release 3 (DR3, Gaia Collaboration 2016, 2023,
Cat. I.355) main catalogue to identify cluster members, extract
optical magnitudes (Gaia G, BP, and RP), and proper motions (pmRAcosDE
and pmDE). We recall that Gran et al. (2019A&A...628A..45G 2019A&A...628A..45G) initially
used the Gaia DR2 (Gaia Collaboration 2018, Cat. I.345) to discover
Gran 1, 2, 3, 4, and 5, which we now update to the DR3 version for the
present analysis.
Finally, two follow-up observing campaigns with the Multi-Unit
Spectroscopic Explorer (MUSE; Bacon et al. 2010, R∼1900-3700) mounted
at the VLT-UT4 (Cerro Paranal, Chile) during ESO periods P103 and P105
were awarded to point at the discovered clusters. The MUSE integral
field unit (IFU) allows us to observe a large number of stars (270-640
objects) in each field with a single pointing using the Wide Field
Mode (WFM, 1 sq. arcmin field of view).
We present Atmospheric parameters for all MUSE Gran 1-Gran 5
analysed stars.
File Summary:
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FileName Lrecl Records Explanations
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ReadMe 80 . This file
table2.dat 83 5 Structural and dynamical parameters derived for
the analysed GCs
tablea.dat 58 172 Atmospheric parameters for all MUSE Gran 1-Gran 5
analysed stars (Tables A1-A5)
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See also:
I/355 : Gaia DR3 Part 1. Main source (Gaia Collaboration, 2022)
Byte-by-byte Description of file: table2.dat
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Bytes Format Units Label Explanations
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1- 7 A7 --- GC Cluster name, Gran 0N
9- 15 F7.3 deg RAdeg Right ascension (J2000)
17- 23 F7.3 deg DEdeg Declination (J2000)
25- 31 F7.3 deg GLON [] Galactic longitude
33- 38 F6.3 deg GLAT Galactic latitude
40- 44 F5.2 kpc dLOS Distance
46- 52 F7.2 km/s RV Mean radial velocity
54- 57 F4.2 km/s e_RV Cluster observational velocity dispersion
59- 63 F5.2 [-] [Fe/H] Median metallicity
65- 68 F4.2 [-] e_[Fe/H] Median metallicity error
70- 74 F5.2 mas/yr pmRA Mean proper motion along RA, pmRA*cosDE
76- 80 F5.2 mas/yr pmDE Mean proper motion along DE
82- 83 I2 --- Nstars Number cluster member stars observed
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Byte-by-byte Description of file: tablea.dat
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Bytes Format Units Label Explanations
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1- 11 A11 --- Name GC-ID, Gran NN-NNN (1)
13- 21 F9.5 deg RAdeg Right ascension (J2000)
23- 31 F9.5 deg DEdeg Declination (J2000)
33- 36 I4 K Teff ?=- Effective temperature
38- 40 F3.1 [cm/s2] logg ?=- Surface gravity
42- 46 F5.2 [-] [Fe/H] ?=- Metallicity
48- 54 F7.2 km/s RV Radial velocity
56- 58 I3 --- S/N Mean S/N were derived for observed GC members
based on their multi-dimensional membership
(RV, [Fe/H], and Kiel diagram)
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Note (1): MUSE Gran 1 labelled Gran 01-NNN, MUSE Gran 2 labelled Gran 02-NNN,
MUSE Gran 3 labelled Gran 03-NNN, MUSE Gran 4 labelled Gran 04-NNN and
MUSE Gran 5 labelled Gran 05-NNN.
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History:
From electronic version of the journal
(End) Patricia Vannier [CDS] 29-Apr-2024