J/A+A/708/A77 Nuclear star cluster at 3pc from Sgr A* (Gallego-Cano+, 2026)
Age and metallicity of the Milky Way's nuclear star cluster studied at
3 pc from Sagittarius A*.
Gallego-Cano E., Schoedel R., Fritz T.K., Hosek M.W. Jr., Muzic K.,
Feldmeier-Krause A., Martinez-Arranz A., Nogueras-Lara F.
<Astron. Astrophys. 708, A77 (2026)>
=2026A&A...708A..77G 2026A&A...708A..77G (SIMBAD/NED BibCode)
ADC_Keywords: Galactic center ; Stars, nearby ; Photometry, infrared
Keywords: Galaxy: center - Galaxy: kinematics and dynamics -
Galaxy: stellar content
Abstract:
The Milky Way's nuclear star cluster (NSC) offers a unique laboratory
for studying the formation and evolution of dense stellar systems
around a supermassive black hole. Previous work suggests that most
stars in the NSC are old; however, the detailed age and metallicity
distributions remain uncertain.
We aim to constrain the star formation history (SFH) and metallicity
of a poorly explored region of the NSC located about 3pc from
Sagittarius A*.
We analysed NACO/VLT observations in the intermediate-band filter
centred at 2.24um, complemented by H-band imaging, and constructed
colour-magnitude diagrams and completeness-corrected K-band
luminosity functions. We clearly identified the red clump and red
giant branch bumps. The SFH was derived by fitting cumulative
luminosity functions with theoretical models from MIST, PARSEC, and
BaSTI, which spans a wide range of ages and metallicities, and by
employing Monte Carlo sampling to estimate uncertainties. We also
constrained the metallicity of the stellar population, further refined
by spectroscopic data from the literature.
The NSC stellar population is predominantly old and metal-rich, with
75.6±9.5% of the stellar mass formed ≳10Gyr ago and a median
metallicity of [M/H]~+0.35. Significant contributions come from an
intermediate-age population around 2-3Gyr (20.8±8.7%), while minor
components appear at ∼400Myr (0.9±0.8%) and 20Myr (3.6±1.4%), the
latter representing a small but non-negligible young population.
Systematic uncertainties related to stellar evolution models, binning,
photometric range, unresolved binaries, and filter selection are
considered.
Our findings indicate that the NSC formed predominantly in an early
episode, with a substantial contribution from a star formation episode
2-3 Gyr ago and minor younger components. The metallicity estimates
are consistent with spectroscopic measurements, and the results agree
with the stellar population properties of the inner NSC and the inner
nuclear stellar disc, providing useful constraints on the transition
between these two structures.
Description:
We present stellar positions and photometry for 2223 stars located
within 3pc of Sagittarius A*. The table contains equatorial
coordinates (J2000) and calibrated IB224-band photometry with
associated uncertainties.
The catalogue provides positions and IB224 photometry for stars
selected after applying the mask described in the paper.
File Summary:
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FileName Lrecl Records Explanations
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ReadMe 80 . This file
table.dat 40 2223 Stellar catalogue
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See also:
J/A+A/502/91 : Proper motions of stars near SgrA* (Schoedel+, 2009)
J/A+A/511/A18 : NIR observations of stars near SgrA* (Schoedel+, 2010)
J/A+A/534/A117 : NIR polarimetry of sources near SgrA* (Buchholz+, 2011)
J/MNRAS/428/2731 : SgrA* emission at 7mm (Beaklini+, 2013)
J/ApJ/820/90 : 4yr 1.3mm VLBI observations of SgrA* with EHT (Fish+, 2016)
J/A+A/618/L10 : SgrA* orbital motions with GRAVITY (GRAVITY Col., 2018)
J/ApJ/863/15 : Spitzer, VLT and Keck NIR light curves of SgrA*
(Witzel+, 2018)
J/ApJ/916/69 : 272-375GHz obs. toward SgrA*'s circumnuclear disk
(James+, 2021)
J/A+A/689/A190 : Photometry of stars around SGR A* (Gallego-Cano+, 2024)
Byte-by-byte Description of file: table.dat
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Bytes Format Units Label Explanations
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1- 10 F10.6 deg RAdeg Right ascension (J2000)
12- 21 F10.6 deg DEdeg Declination (J2000)
23- 31 F9.6 mag IB224 Calibrated IB224 magnitude
33- 40 F8.6 mag e_IB224 Uncertainty in IB224 magnitude
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Acknowledgements:
Eulalia Gallego-Cano, lgc(at)iaa.es
(End) Patricia Vannier [CDS] 03-Mar-2026