J/ApJ/944/79 Star Formation History of the Milky Way's NSC (Chen+, 2023)
The star formation history of the Milky Way's Nuclear Star Cluster.
Chen Z., Do T., Ghez A.M., Hosek M.W.J., Feldmeier-Krause A., Chu D.S.,
Bentley R.O., Lu J.R., Morris M.R.
<Astrophys. J., 944, 79 (2023)>
=2023ApJ...944...79C 2023ApJ...944...79C
ADC_Keywords: Galactic center; Stars, late-type; Abundances; Spectra, infrared;
Photometry, infrared; Milky Way
Keywords: Galactic center ; Star formation ; Galaxy formation ;
Milky Way formation ; Infrared spectroscopy ; Adaptive optics ;
Adaptive interferometry
Abstract:
We report the first star formation history study of the Milky Ways
nuclear star cluster (NSC), which includes observational constraints
from a large sample of stellar metallicity measurements. These
metallicity measurements were obtained from recent surveys from Gemini
and the Very Large Telescope of 770 late-type stars within the central
1.5pc. These metallicity measurements, along with photometry and
spectroscopically derived temperatures, are forward modeled with a
Bayesian inference approach. Including metallicity measurements
improves the overall fit quality, as the low-temperature red giants
that were previously difficult to constrain are now accounted for, and
the best fit favors a two-component model. The dominant component
contains 93%±3% of the mass, is metal-rich ([∼0.45),
and has an age of 5_-2-+3Gyr, which is ∼3Gyr younger than earlier
studies with fixed (solar) metallicity; this younger age challenges
coevolutionary models in which the NSC and supermassive black holes
formed simultaneously at early times. The minor population component
has low metallicity ([~-1.1) and contains ∼7% of the
stellar mass. The age of the minor component is uncertain (0.1-5Gyr
old). Using the estimated parameters, we infer the following NSC
stellar remnant population (with ∼18% uncertainty): 1.5x105 neutron
stars, 2.5x105 stellar-mass black holes (BHs), and 2.2x104 BH-BH
binaries. These predictions result in 2-4 times fewer neutron stars
compared to earlier predictions that assume solar metallicity,
introducing a possible new path to understand the so-called
"missing-pulsar problem". Finally, we present updated predictions for
the BH- BH merger rates (0.01-3Gpc-3/yr).
Description:
A spectroscopic survey of a sample of 83 late-type stars (F type or
later) within a radius of 1pc from the central supermassive black hole
(SMBH) yielded metallicity measurements, [M/H], for all of those stars
(Do+ 2015, J/ApJ/809/143; also see details in
Stostad+ 2015, J/ApJ/808/106). The original spectra were obtained with
the medium-spectral-resolution Near-Infrared Integral Field
Spectrograph (NIFS) on the Gemini North telescope with the
natural-guide-star and laser-guide-star AO system ALTtitude conjugate
Adaptive optics for the InfraRed (ALTAIR). NIFS provides the observed
spectra in the K broadband filter (1.99-2.40um) with a spectra
resolution of R∼5000 and a spatial resolution of 115-165mas. The
observations between 2012 May and 2014 May span a projected radius of
8'-22" (0.3-0.9pc) from Sgr A*, covering a total surface area of
81arcsec2, approximately 0.15pc2 at a distance of 8kpc.
See Section 2.1.
Metallicity determinations were made by
Feldmeier-Krause+ (2017, J/MNRAS/464/194) using a spectroscopic survey
of 687 late-type stars within a radius of 1.5pc from the central
SMBH. The original spectra were obtained with seeing-limited
observations using the medium-resolution integral-field K-band Multi
Object Spectrograph (KMOS) at the Very Large Telescope (VLT) in the
K-band filter (∼1.934-2.460um). The spectral resolution, R, varies
between 3310 and 4660 for 23 different active integral field units
(IFUs) on the KMOS detectors with a standard deviation of 300 over all
IFUs. The observations on 2013 September 23 covered an area of
2700arcsec2, approximately 4pc2 at a distance of 8kpc.
See Section 2.2.
File Summary:
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FileName Lrecl Records Explanations
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ReadMe 80 . This file
table10.dat 87 83 AO observations
table11.dat 82 687 Seeing-limited observations
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See also:
J/ApJ/597/323 : Cool stars at the Galactic Center (Blum+, 2003)
J/ApJ/675/1459 : Compact Binary Coalescence Galaxy Catalog (Kopparapu+, 2008)
J/ApJ/703/1323 : Sp. of stars in the Galaxy's nuclear cluster (Do+ 2009)
J/A+A/511/A18 : NIR observations of stars near SgrA* (Schoedel+, 2010)
J/A+A/535/A42 : Metal rich stars in solar neighbourhood (Trevisan+, 2011)
J/A+A/549/A147 : Abund. of microlensed bulge dwarf stars. V. (Bensby+, 2013)
J/A+A/564/A125 : AGN Torus model comparison in the CDFS (Buchner+, 2014)
J/A+A/570/A2 : Spectra and RVs of nuclear stars (Feldmeier+, 2014)
J/A+A/566/A47 : MW nuclear star cluster extinction map (Schoedel+, 2014)
J/ApJ/809/143 : K-band sp. of stars within central 1pc of the MW (Do+, 2015)
J/A+A/584/A2 : KMOS view of the Gal. centre. I. (Feldmeier-Krause+, 2015)
J/ApJ/808/106 : NIR sp. obs. in the Galactic Center (Stostad+, 2015)
J/MNRAS/457/2122 : Nuclear star clusters photometric masses (Georgiev+, 2016)
J/MNRAS/464/194 : Metallicity distribution in the GC (Feldmeier-Krause+, 2017)
J/A+A/610/A83 : GALACTICNUCLEUS: JHKs imaging survey (Nogueras-Lara+, 2018)
J/MNRAS/494/396 : Metallicity distribution in GC (Feldmeier-Krause+, 2020)
J/A+A/641/A102 : MW nuclear star cluster HKs photometry (Schoedel+, 2020)
J/MNRAS/513/5920 : Stellar Populations of NSC and NSD (Feldmeier-Krause, 2022)
Byte-by-byte Description of file: table10.dat
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Bytes Format Units Label Explanations
--------------------------------------------------------------------------------
1- 9 A9 --- [SDM2015] Name (1)
11- 20 F10.6 deg RAdeg [266.4/266.5] Right Ascension (J2000)
22- 31 F10.6 deg DEdeg [-29.1/-29] Declination (J2000)
33- 37 F5.2 mag Ksmag [10.44/16.67] Ks-band magnitude (2)
39- 42 F4.2 mag e_Ksmag [0.01/0.2] Uncertainty in Ksmag
44- 48 F5.2 mag Hmag [12.57/18]? H-band magnitude (2)
50- 53 F4.2 mag e_Hmag [0.01/0.04]? Uncertainty in Hmag
55- 58 F4.2 mag AKs [2.3/3] Extinction correction at Ks-band (2)
60- 63 I4 K Teff-CO [2980/4851] Effective temperature from CO (G1)
65- 67 I3 K e_Teff-CO [164/176] Uncertainty in Teff-CO
69- 72 I4 K TeffS [3447/4613] Starkit-derived effective
temperature (G2)
74- 76 I3 K e_TeffS [413/425] Uncertainty in TeffS
78- 82 F5.2 [-] [M/H] [-1.27/0.96] Metallicity (G2)
84- 87 F4.2 [-] e_[M/H] [0.3/0.4] Uncertainty in [M/H]
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Note (1): Name from Stostad+ 2015, J/ApJ/808/106
Note (2): H- and Ks-band photometry and AKs extinction taken from
Schodel+ 2010, J/A+A/511/A18; see section 2.
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Byte-by-byte Description of file: table11.dat
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Bytes Format Units Label Explanations
--------------------------------------------------------------------------------
1- 5 I5 --- [FNS2015] [1/25496] Name (1)
7- 15 F9.5 deg RAdeg [266.4/266.43] Right Ascension (J2000)
17- 26 F10.6 deg DEdeg [-29.02/-28.9] Declination (J2000)
28- 32 F5.2 mag Ksmag [9/16.44] Ks-band magnitude (2)
34- 37 F4.2 mag e_Ksmag [0.01/1] Uncertainty in Ksmag
39- 43 F5.2 mag Hmag [11.7/19.01] H-band magnitude (2)
45- 48 F4.2 mag e_Hmag [0.01/1] Uncertainty in Hmag
50- 53 F4.2 mag AKs [2.3/3.6] Extinction correction at Ks-band (2)
55- 58 I4 K Teff-CO [2181/5466] Effective temperature from CO (G1)
60- 62 I3 K e_Teff-CO [163/854] Uncertainty in Teff-CO
64- 67 I4 K TeffS [2300/5297] Starkit-derived effective
temperature (G2)
69- 71 I3 K e_TeffS [205/463] Uncertainty in TeffS
73- 77 F5.2 [-] [M/H] [-1.25/1] Metallicity (G2)
79- 82 F4.2 [-] e_[M/H] [0.24/0.4] Uncertainty in [M/H]
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Note (1): Name from Feldmeier-Krause+ 2017, J/MNRAS/464/194
Note (2): H- and Ks-band photometry and AKs extinction taken from
Schodel+ 2010, J/A+A/511/A18, Nogueras-Lara+ 2018A&A...620A..83N 2018A&A...620A..83N and
Nishiyama+ 2006ApJ...638..839N 2006ApJ...638..839N; see section 2.
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Global notes:
Note (G1): Effective temperature as derived from the calibrated Teff-EWCO
relation; see Appendix B for details.
Note (G2): Effective temperature and metallicity derived from full spectrum
fitting using the STARKIT code, Kerzendorf & Do 2015zndo...1117920K 2015zndo...1117920K
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History:
From electronic version of the journal
(End) Prepared by [AAS], Emmanuelle Perret [CDS] 27-Jan-2025